The last version of UltraSn0w was supposed to fix a number of bugs and overall, it did a great job. However, some people are still having issues. The Dev Team posted an article with a few ultratips for those of you still having problems with your unlock.
- Battery draining too fast? It’s probably because you restored your iPhone from backup. You should restore your iPhone and set up as a new phone.
- Issues with T-Mobile? T-Mobile’s 3G doesn’t work on the iPhone. It’s a frequency issue. Simply deactivate 3G in Settings > General > Network
I think these two are the most common issues after unlocking. For more information, I suggest you hop over the Dev Team’s blog and read the full article.