Working, But Getting Error Message... Options

[callingguides]

Although my ads seem to be working with OpenX Hosted, I keep getting messages such as this when I'm working with blocks:

"The block OpenX Zone 8959 (125x125-VoIP6) was assigned to the invalid region left and has been disabled."

I don't have a 'left' region and am not attempting to assign any block to said region.

As I say, my ads appear to be running properly, but I'd still like to clear up the issue if possible.