Getting Time Machine backups working with an Iomega Home Cloud Edition NAS

I'm getting some strange behaviour from Time Machine since upgrading to Moutain Lion using the Iomega Home Cloud Edition NAS as the end point for the backups.

Getting the first backup to complete took some effort and the problem I'm facing now is that automatic backups don't start.

When I right click the menu bar icon and select Back Up Now I get the following error from Time Machine:

Time Machine couldn’t complete the backup to “iomega”. The backup disk is not available.

If I go in the Time Machine preferences however and do the same thing by right clicking the drive icon, the backup starts just fine.

What's strange is that the backup drive is properly mounted and there are 2 separate behaviours depending on where I start the backup from.

How can I get Time Machine backups working automatically with this setup?

It seems that TM is looking for an other/older backup drive. You can check it in TM preferences, under select disks panel. If you have 2 entry disk, remove the one you don't use.