iPad 2 locked by Apple?
I believe this is associated with automatic downloads and/or iTunes Match. See http://support.apple.com/kb/HT4627


  Once a device or computer is associated with your Apple ID, you cannot associate that device or computer with another Apple ID for 90 days.


This article makes it sound like you can only sign in with a different account every 90 days, but this doesn't seem to be the case in my experience. I regularly sign into different accounts on our family's iPad when downloading apps and this has never been a problem.

I've only gotten warnings regarding this 90-day lockout when enabling iTunes Match.

The article also notes that:


  Note: Removing a device from your Apple ID does not override the 90 day timer. The timer must complete 90 days from the day the device was associated before it can be associated to another Apple ID.


It looks like you'll have to contact Apple if you want to have the device reset.