I disagree, I use go launcher and the problem was still their. Yes, the stock launcher does not rotate, but the phone will not rotate in any apps or even the system settings.
I might have a fix though,
(And though i heavily doubt it will do anything bad to your phone, understand that you are trying this at your own risk)
1) I downloaded "Inclinometer Free" from the market,
2) opened the app
3) Press the menu button
4) held my phone in landscape mode untill the numbers were zero
If you can't get into landscape mode do a restart.
5) Pressed Calibrate
6) I did the same thing in portrait mode
I did this many hours ago and my rotation still works.
I'm not at all claiming this is a fix yet because its only been 6 or so hours.
But it used to only take a couple of hours to start screwing up, so hopefully we got something here.
I will leave my phone on and test the rotation every so often. If the problem comes back, you guys will be the 1st to hear about it