Before restoring and setting up as new (without backup) just for test purposes. Be sure to transfer purchases to the computer and backup. Don't want you to lose anything ;)
If the issue persists after setting up as new, it's hardware and it needs service.
Because it happened RIGHT AFTER the update it sounds like something weird happened during the update. If the issue is resolved after setting up as new restore from backup. If the issue comes right back you'll need to import pictures and any other important data, then restore as new, and the sync that content over. The one thing you'll if you need to sync is text messages.
Resources below will ensure your data is safe.
http://support.apple.com/kb/HT1848
http://support.apple.com/kb/HT1414
Cheers!