My wife and I both have the Galaxy S2 T989 (T-Mobile). Both purchased like new off eBay. When I got hers a couple months ago, as soon as I got it I factory reset and wiped the caches, upgraded to JB via Kies, and then turned right around and rooted it via Odin using the instructions found on galaxys2root.com. Everything went flawless, took me less than a half an hour total for everything. I got mine a couple months later and did the exact same process as soon as I got it in the mail. However after rooting on Odin and getting the green pass just like hers, it got stuck in a boot loop when it rebooted. It would go as far as the "galaxy S2" splash screen, and sometimes past that to where the Android takes off, then reboot, or freeze. It then became unresponsive to any button pushes and I had to pull the battery to get it to shut off (The battery is a new OEM Samsung battery incidentally). I ultimately had to unroot, re-install ICS and re-upgrade back to JB via Kies again to get out of the loop. I did this whole process 3 times to make sure it wasn’t something I did. So I’m still running unrooted with JB on it now.
The only thing I noted that was kinda odd was that when I open Rom Manager in my current non rooted state, it shows that I already have CWM and TWRP installed on it. Even though when I go to recovery mode it's the standard OEM Samsung menu. I never installed TWRP, and CWM was only on it for a bit when I was in the boot loop. Could this be my issue? Are they both still somewhere on my phone interfering with each other and I can only see them via ROM manager?
Sorry for such a long first post, and thanks in advance!