HTC includes something that logs application crashes to a file called anr_history.txt and no mechanism to limit how large this file gets. After having my phone for almost 18 months, this file had grown to over 600mb, which was more than 50% of the available internal storage. With total free space below 110mb, the phone began to malfunction including email no longer syncing and all application updates failing.
To resolve this issue, empty the crash dump file using adb:
$ cd /data/data/com.android.htcprofile $ ls -l # see how big the file is before clearing $ echo // > anr_history.txt $ ls -l # verify the file has been emptied * Turn off USB debugging again
This can be done on a stock unit. No root or custom roms are required.
Instructions for solving this issue were compiled from various threads on xda-developers forum.