WinXP, Filemaker 8.5 Adv

When working with fm I experience strange keyboard trouble. Especialy during
field definition, but sometimes also during normal use. It all starts good.
but without notice some keys of the keyboard display different signs. What
used to be a * now becomes a (. The ( becomes a ), { becomes <, etc etc. All
normal letters remain normal. The only remedy seems to shut-down filemaker
and re-open the file. Sometimes it happens after an hour, but sometimes also
after five minutes. (And then again after a couple of minutes). Generally I
have no other programs running (exept the system ofcourse). But when I try
these don't have the same trouble. So it seems filemaker only. Any idea's?

Ursus