Hey-
I am a tech support rep at www.cellswholesale.com and would love to help! I think that the issue you are facing could be due to a early firmware issue that was occuring on some N93's......The issue can actually be fixed if you master reset the phone, but unfortunately some of your files could be deleted.....Also, there could be a complicated fix to this, but I think the fastest way to do it would be just to master reset..
Hope I was some help to you!