I got an email report this morning saying this:
It looks like the same issue as this thread, but since the OMV release is different, I thought it would be better to have another dedicated thread.
I am guessing this issue has to do with the release of Jessie which is the new stable as of yesterday. I have replaced "stable" with "wheezy" in the file /etc/apt/apt.conf.d/99openmediavault-release and now omv-update command doesn't show any issue.
Does anyone else got this problem?
edit
See here for the solution:
By the way, this is only affects systems upgraded from 0.5. Just remove apt.conf rm -f /etc/apt/apt.conf and it should be fine. The file isn't used anymore.