GSM Nexus S ICS problem - password screen after making a call?

Hi, I just installed the proper ICS release on my GSM Nexus S. It's unrooted, just unlocked how you buy it in the store. Whenever I make a call on the phone, immediately after hanging up, it immediately asks for my password again.

I also have a Galaxy Nexus, and on that phone I just get dropped back into the People app as expected. I tried changing the security on the Nexus S from password to pincode and swipe gesture but it doesn't make a difference. it's quite annoying to be honest.

Does anyone have the same problem?