I'm running 1.1.4 and on a launch day phone so it may not work with later bootloaders, althout I can' see why not.

A couple of times when adding theme files my phone would get stuck with an endlessly spinning wheel; not even forcing a reset would fix the problem as it stays on the apple logo with the spinning wheel. The first time I did a full restore, thinking that it was completely botched, which is a big hassle. Turns out there is a far easier fix.

Most importantly make sure you have OpenSSH v4.6p1-2 installed. This is the version that is always on, but doesn't drain your battery because it only starts the processes once it receives a query. Even if you restarted your phone and are stuck at the logo screen with the spinning wheel you can sFTP into the phone at that point, assuming your wifi is on. I'm assuming at that point everything has come online and the phone is just trying to pull up your springboard.

If you regularly turn your SSH or WiFi off you are out of luck.

There are two things you can do.

1. Delete, via sFTP, the files you just added. This can be a little random since you may not know which files are corrupt. Lets say you just uploaded a theme folder but when you restarted the springboard to that theme you just get the spinning wheel. Not even restarting the phone helps because the phone will crash at startup when it tries to access the bad files. If you delete the entire theme folder then the phone will free itself back up to the lock screen without even needing a restart. Just swipe to unlock and everything will be fine, albeit with the default icons.

2. Delete the following file and restart:

var > mobile > Library > Preferences > com.apptapp.SummerBoard.plist

This is the file that tells SMBprefs which theme to load and once deleted the phone will display the default graphics thus avoiding a crash because the corrupted files don't load. This method requires you to restart the phone once that files is deleted since the fix happens on boot.

This has saved me a ton of effort as my phone has crashed a couple of times in this manner.