I had an issue entering the serial number into FB4 in Windows. One of the 4-digit groupings in my SN starts wtih 40. When I type 40 into that box, initially the 4 appears, and then as soon as I type 0, the 4 disappears. Weird, I know. I ultimately was able to enter the SN by copying/pasting it into the registration dialog, but typing it in manually was not possible.