The received wisdom on JB Priestley used to be, roughly speaking, that he was a straightforward, naturalistic plodder - even when he strayed into metaphysics, as in all those time plays, it was metaphysics of a very unsubtle, one-dimensional sort. Then Stephen Daldry exploded that notion with his extraordinary production of An Inspector Calls, demonstrating that what we'd taken for decency and social conscience was actually a kind of rage, that a surface of West End orthodoxy hid an expressionist intensity of gesture. After that, it was hard to take anything Priestley said at face value.

So in a way it's refreshing to come across Jude Kelly's production of When We Are Married at Chichester, which could have been designed expressly to convince you that this play, at any rate, is exactly what it looks like: a straightforward, cheerful Yorkshire romp.

I'm not persuaded on any count, not even the Yorkshire bit, for all that "On Ilkla Moor baht 'at" reverberates through the action. The cast all seem to have different ideas of what constitutes a Yorkshire accent, and Roger Lloyd Pack, who plays the pompous, speechifying Albert Parker ("Councillor Parker"), has several, none of them good ones. With the geography of the piece wobbling about all over the place, even Paul Copley, the thinking man's Brian Glover, sounds unconvincing at times.

The cheerfulness seems pretty debatable, too. True, there's a happy ending, all marital confusions straightened out, and the three squabbling couples finding a new harmony; but we've been given a distinctly sour view of matrimony up till then. Priestley seems to regard marriage purely as an institution for containing sexual conflict: he shows us one marriage, the Parkers (Lloyd Pack and Annette Badland), where the husband dominates and the wife is cowed into perpetual submission; one, the Soppitts (Copley and Dawn French), where the position is reversed; and one, the Helliwells (Gary Waldhorn and Alison Steadman), where a rough equality is achieved only through a delicate balance of hostility.

Ibsen in one of his more depressive moods might have recognised in Priestley a soul-mate - and you might trace echoes of A Doll's House here in the way these marriages are torn apart when they turn out to be based on a fiction. There's an even stronger recollection of The Lady From the Sea. In that play, you may recall, Ellida can't be happy until her husband releases her from her vows; once the marriage is based on her free consent, everything goes swimmingly. Here, the revelation that the clergyman who married all three couples on the same morning 25 years ago was not properly qualified, and hence they are not legally tied, provides the opportunity for them to redefine their marriages, to achieve a new sort of harmony.

Like Ibsen, Priestley shows marriage and the family as an integral part of the apparatus of bourgeois respectability and social stability. As in An Inspector Calls, the revelations that most threaten the family come from below: it's the Helliwells' bolshie housekeeper, Mrs Northrop, who spreads the news of impending disgrace, the seaside tart Lottie Grady who makes it clear how far one marriage, at least, has become a sham. A threat to matrimony and a threat to the social order come as very much the same thing.

I'm not saying that every Priestley play should be played as searing social critique; but in glossing over the implicit social comment, in trying to put it across as straightforward farce, Kelly doesn't give her cast enough to get hold of. At any rate, several seem lost for something to do - Dawn French, for one, reduces pushy Clara Soppitt to not much more than a set of grumpy expressions, and there are a couple of points where she seems to be floundering for direction. Even Alison Steadman, who you imagine can do this sort of thing wrapped in a sack, is a little underpowered.

The best acting is in the supporting roles: Elizabeth Chadwick's nervously excited maid, Dora Bryan's gleefully destructive Mrs Northrop, and Leo McKern's crapulous photographer - at times he struggles to make himself heard, but as far as comic timing and grasp of character go, he and Bryan act the socks off anybody else on stage.

More dark undercurrents at the Open Air Theatre in Regent's Park, where Paint Your Wagon opened last week. The plot, if that's not too strong a word, of Lerner and Loewe's musical revolves around alcoholism, sexual deprivation, the commodification of sex and the never-quite-stated threat of rape. The action takes place in Rumson Town, a California gold-mining community of 700 men and one female, Jennifer Rumson, a girl on the cusp of womanhood. The other miners demand that her father send her away "before something happens"; she doesn't want to leave because her alcoholic father can't look after himself, and she's in love with a young Mexican (horror at the prospect of miscegenation is a theme hinted at but never followed up). A Mormon with two wives is made to auction off the spare; she eventually leaves her new husband for somebody with sounder financial prospects. There's a brief boom, with a dancing-hall and good times for all, but then the gold runs out and the town is pretty well abandoned.

Ian Talbot's production doesn't make much of the subtext, but has enough rough-and-ready vim to get away with it, and while the score isn't fantastic it does have "They Call the Wind Maria" and "Wand'rin' Star". My only serious beef is that Claire Carrie is miscast as Jennifer - she's not girlish so much as short, and her protestations of innocence are very jarring.

And yet more darkness in the National's new children's show, The Red Balloon. Translating a wordless, short film into a two-hour musical is fraught with difficulties: for one thing, half the charm of Albert Lamorisse's original lay in the fact that the balloon's behaviour was never explained or commented on. Once the strangeness has been given a name, even a name as vague as "magic", a lot of the charm has gone. And in expanding the story, Anthony Clark has steered the emphasis away from young Pascal's relationship with the balloon towards his relationship with his schoolmates, who come across as a bunch of extras out of Lord of the Flies (or Blue Remembered Hills: the children are played by adults).

My nephew Joseph, who's five in September, found some of the bullying terrifying, but liked the singing and dancing and, pressed for a verdict, said he would certainly advise mummies and daddies to take their children. Personally, I found the music and lyrics set my teeth on edge, but most people would probably take Joseph's word on this one.

Which leaves virtually no room to say anything about Art-Inter Odeon's Romanian-language Murder in the Cathedral, at the Almeida until Saturday - something of a relief, because I haven't much to say. As with any production where you don't understand the language, astonishment - at the way Eliot's vision of a broken, scarred land is fleshed out, at the sheer freshness of approach - is mixed with bafflement. Two things shine out, though: Marcel Iures is a magnetic actor; and the play doesn't, frankly, lose a lot in translation.

Theatre details: Going Out, page 14. Robert Butler returns next week.