I am not sure why, but Armory will show inaccurate balances for me if I leave it open for a week or 2 at a time. I do a re scan of databases and then let it go (takes 1 hour) then it shows correct balances again.

Armory : 0.29.3=Beta
Core .0.9.3
Windows 7 x64

Just wondering if this is known to happen often or it is something else.