Never heard of the exact problem you are having. I have a 3GS, 4 and 4S in my possession and iOS 5 works great on all.
Try restoring again, this time download the latest iOS 5.0.1, there was an update to the one for 4S due to a "no SIM found" issue. Not the same issue you are having but close, but afaik the fix was only made for 4S.
Fix “No SIM Card Installed” Error on iPhone 4S by Installing iOS 5.0.1 Build 9A406