I have the Nexus S, Android 2.3.6 with a build number GRK39F. I'm on T-Mobile in the UK.
Today I've been experiencing a phone freeze where once the screen locks, its impossible to get it out of lock mode. The only solution was to remove the battery and replace and try turning it back on again. This also only works sometimes and I need to keep removing and reinserting the battery to get it to work. I've increased the screen display time to 30 mins, but all that means is that the phone has to be taken apart every 30 mins rather than every 2 mins.
I'm running the 2.3.6, which seems to be the newest OS for which this is happening. I'm also still patiently awaiting my ICS update, but obviously have no time for when that is due.