iPhone 4 32GB with iOS5 just recently been freezing on an unlock slide every third or fourth time

I upgraded to iOS 5 the evening it came out. I've just recently been experiencing freeze ups on the unlock home screen before I type my passcode. It'll sit on the unlock screen for a couple of mins before turning off and going to the spinner in the middle of the screen and that even freezes and locks up. The only way I can get my phone back is to do a hard (power+home button) reset or else it'll sit there for hours with the spinner not moving on a black background. I've not changed anything in the OS after configuring it the first night iOS 5 was out. It's been fine since with no issues until today. Any ideas?