This has to do with one of several system bugs on non-volatile file system the T5, Treo650, and some newer handhelds. After a copy to a card fails (for whatever reason), the system becomes unstable until you soft reset. This causes other future files to fail for no reason. We think the system leaves some file handles or temporary work buffers free after a failed copy.
If you run into such a failure, and you genuinely have enough space on the card, use the detailed log feature to track down the errant file and try adding it to your exclusion list. Some files cannot be backed up because the system or applications are accessing them in the background.
Also, newer devices with non-volatile (NVFS) memory shuffles memory after copying several megabytes, and this causes background apps to crash if they have not been specifically patched for NVFS. Our own TealMaster, TealLock, and TealScript had to be revised recently to account for this, so if you have any of these apps, make sure you are running the latest versions and try turning off all other background apps before a backup to determine if you might be running one such app that still needs to be patched.
If this is the case, you'll need to track down which app is problematical by turning off your background apps, hacks, and drivers one-by-one until the problem goes away. Once you've identified it, you might be able to fix the problem by adding those applications to TealBackup's "lock" list using the "Lock Application" feature under TealBackup preferences. The best solution, however, is to contact its developer for an NVFS-compatible version.