WHEN it comes to gentle comedy, you can always trust the man who provided the voice of Slimer.

And now, five years after his last film Evolution, Ivan Reitman is back with this sweet, slight slice of merriment, which provides an interesting alternative to all of the more straightforward superhero fare of the summer.

Uma Thurman plays the titular ex, who's chatted up by Matt Saunders (Luke Wilson) on the train one day while in her non-super state as Jenny Johnson.

Brunette, bespectacled and behaving herself, she seems like a safe bet for Matt, who's desperately trying to secure a girlfriend to help him get over the fact that he's in love with his co-worker, Hannah (Scary Movie's Anna Faris).

From the off, he senses that Jenny's a little crazy, but puts his concerns aside when they spend a mind-blowing (and room destroying) day in bed.

His feeling that something's not quite right is finally confirmed when Jenny reveals that she's actually stunning blonde super-heroine G-Girl.

Despite this fact, however, her neediness and crazed jealousy lead him to dump her, and Jenny begins to use her powers to ruin his apartment, his car and his life.

Hell hath no fury, indeed, and things escalate to dangerous levels when she then discovers he's started seeing Hannah.

Can things possibly end happily for all sides of the love triangle?

By a country mile, the best thing in this movie is the gorgeous and disarming Uma Thurman, who throws herself into her role with abandon, relishing the opportunities provided by a character for whom the term "bunny boiler" is rendered redundant. It doesn't even begin to cover it.

Her "ordinary" self recalls her performance as Poison Ivy in Batman and Robin, but that doesn't imply a criticism.

It's simply that she's prepared to embrace every facet of a nutty role again, and an audience cannot help but yearn for her to have a happy ending, despite the fact that she throws sharks into people's bedrooms.

The one duff note comes courtesy of Eddie Izzard as uber-villain Professor Bedlam, who is from Jenny's past and has a nasty wish to take away her powers.

Eddie may be a comedic genius as far as stand-up is concerned, but the man cannot act, despite his having racked up countless performances in endless big movies.

Thankfully, this doesn't ruin the rest of the concoction.

There are few better directors of this sort of material than Reitman, whose wonderful Dave is one of the most underrated comedies of the 1990s, and he doesn't hit a wrong note throughout.

It's also great to see a super woman in control, after all the fuss about Batman, Superman and Spider-Man, and the abject failure of Catwoman. Get this foxy female a sequel!

A lovely cast, funny jokes, great role reversal and a happy ending combine to ensure that this movie will have you smiling all the way home.