backintime - "Done, no backup needed" on changed files

When started from the terminal (backintime-gnome), pressing "Take snapshot" for profile "tst" (in the GUI, obviously), I get on the terminal:

INFO: The application needs to change the backup format. Start the GUI to proceed. (As long as you do not you will not be able to make new snapshots!)
WARNING: Backup not performed

I removed the backintime destination directory, as well as ~/.local/share/backintime and ~/.config/backintime

Try 0.9.99.37 - sounds like bug 575022

Thanks Dave, but it won't even run for me:

ii backintime-com 0.9.99.37 Simple backup system (common)
ii backintime-gno 0.9.99.37 Simple backup system for GNOME Desktop

$ backintime-gnome
Traceback (most recent call last):
  File "/usr/share/backintime/gnome/app.py", line 41, in <module>
    import backintime
ImportError: No module named backintime

I used
"bzr checkout lp:backintime"
(how about adding a note for this on the project's Download-page, I had to look around the launchpad site, but even this left me guessing how to get the up2date version)
"makedeb.sh"
"dpkg -i backintime-common backintime-gnome"

How does one install this?

You can use testing repository. You get informations here: http://backintime.le-web.org/download_page/

im using Back In Time 1.0.10, backup works on one external drive but dosent anymore on the other. "Done, No backup needed"
"WARNING: Backup not performed". Files have changed.

I had this problem on Ubuntu 14.04 with BackInTime 1.1.2 and upon restart SSH+Encrypt worked.
I believe it is to do with the mount file system that BackInTime holds open. At some point it fails to diff I think and hence does not run the backup. Logging off and back on again kills the mount and the "re-attach" allows diff to work.
I can't confirm this is the case but it is my "best guess".

By now this 'Done, No backup needed' message is more like an educated guess which will most likely fail if there was an other problem somewhere in the chain. I'm already thinking about introducing a proper interprocess communication between GUI, running snapshot and systray icon. That should eliminate those false positive messages. But nothing done yet.

BTW there is no diff anymore ;-) It's done by 'rsync --dry-run'

I think I have the same problem. In the GUI, when clicking "Take snapshot", I get a "no backup needed". In the terminal, I get "The application needs to change the backup format. Start the GUI to proceed."

What can I do please?

Arghh, this affects all my backups. I can't backup anything anymore

Did you empty the Host/User/Profile-ID lines in Settings? This will also cause 'No backup needed' (I added a test to prevent this in next version)

Run 'backintime --backup' from command-line and post the output in a new question please.

You are right. I put Host/User/Profile-ID back and my backups seem to work again. Thank you.