Actually, the bug I was talking about refers to the "Invalid Date" appearing in the TEBE message, not about TEBE being unresponsive. You said that the unresponsiveness appeared after you click "Cancel"? That shouldn't be. Are you getting any TEBE related errors in the error console (
Tools > Error Console)? You may also want try the extension for error checking. It is more comprehensive.
Also try running "Clear TEBE preferences" and "Verify extension directory" in
Tools > TEBE > TEBE Options > Debug.If you are still experiencing problems, try this: Open and clear the Error console. Leave it open and perform a backup. When (or if) the backup completes, examine the error console for any error messages. Copy/paste them here.
If TEBE is timing out with a "Script is busy" or "Unresponsive script" message, you should increase the wait time in Tb preferences. To do this, go to
Tools > Options > Advanced > General > Config Editor. Paste
dom.max_chrome_script_run_time into the filter box. If the value of this preference non-zero but less than 60, change it to 60. This is number seconds Tb will wait before declaring a script is not working (zero means wait forever). If your backup is around 2GB (which is HUGE!), you may have to set the preference to zero.
The TEBE results report will list disabled extensions only when running a selective backup. The disabled extensions are marked with special icon (as in the
DOM Inspector extension here):

Of course, Tb will always be unresponsive when a backup is occuring. Since your backups will tend to be very large (and hence take quite awhile to complete) you may want to consider not using a scheduled backup. Instead, you could perform a manual backup once a week when you won't be actively using Tb. You could set a reminder for 7 days in
TEBE Options > Schedule > Backup reminder.