I know there are issues with the scroll bar in classic DBA. I suspect it is related to the number of part numbers in the inventory file and data buffer overflow. John (Shadowcaster) is in electronics industry, they have LOTS of part numbers.
May also be a Classic/Evolution memory management issue - Karen has Evo, John doesn't - Hey, John, maybe it's time to try the free 30 day trial

Be interesting to see if it makes a difference.