Yesterday I took a nandroid backup of my stock GB rom (4.5.608) as I was going to install CM7. I was disappointed of CM7 as it generated a lot of FCs. I SBF'd and installed stock GB again, and installed 4.5.608. I tried to restore the nandroid backup from CWM and it failed at the last step, showing that an error was encountered while formatting /system. What could the problem be? Could it be a corrupted backup?
Edit: I took another backup today and went to restore it immediately after and it still told me that it could not format /system. What's wrong with my phone?