1. If you just bought an iPad 2 from Apple, it should have come with 5.0. You can check this out by going to the About section found under the Settings app on your iPad.
2. If you do not have 5.0 as you suggested, and it is causing the error which you suggested, then you should stop by the Apple store for them to check it out.
This sort of issue is hard to diagnose on a forum as no one can really see anything happening.