Hmm, I've never had a problem with my sony ericsson, I have a Z310i.
Did it happen after a software update?
I have the W810i, and no, i haven't had any problems. Sometimes i feel like there's a little bit of lag when opening a menu, but that's not very often.
To see a World in a Grain of Sand
And a Heaven in a Wild Flower
Hold Infinity in the palm of your hand
And Eternity in an hour