The speed of the server is irrelevant to the fox problem. It occurs when a computer executes FPW I.E. workstations. You don't need to worry about the speed of the server.

Secondly, there are several reasons more or less likely to produce the difference in operation between a 450 and a 550. Video adaptor, driver, DLL version, more or different background tasks running, etc... I have no clear idea of why. Maybe the FPW 2.6a build is different, I don't know. All I know is that both machines have FPW 2.6a, have the patch applied and FPW fails on my machine more often than not, but did not fail in the three of four tests I ran on the other machine.

HTH