I've had a few problems similar to this (generally unresponsive every now and then), but mainly the content manager would run continuously after a sync until the battery went flat and I got into the habit of killing it right after each sync.
I suspected a corrupt epub, but couldn't find an easy way to work out what the content manager was looking at so I put the following in a script (my T1 is rooted):
busybox find /proc/*/fd -print0 | busybox xargs -0 ls -l | busybox grep epub
This just looks for any open epub files that a process has open.
Once I found an epub that the content manager was stuck on, testing it with "unzip -t" would give errors like:
I've fixed this (so far!) by doing a number of cycles of bad sector scan/fix. On Windows 7 with the T1 connected, right click Properties, select the Tools tab, click "Check now" and then check the "Scan for and attempt recovery of bad sectors" box and then click Start. Anything that was listed as having a bad sector/cluster I then got Calibre to re-send to the T1.
If I have any more errors, I think I'll just switch to using a micro SD card and not put anything in the internal memory of the T1. What I'm really worried about is if any of these bad sectors occur in other partitions of the T1's memory - then I suspect it'll be time for a new reader...