Interestingly enough, all I am ever using is a Mac machine on currently OS X 10.5.7. Our suspicion is that these problems that some Macs have may be related to USB drivers on the Mac platform. The latest OS X update (10.5. was released not too long ago. While we have tried to replicate any problems with both 10.5.8 and 10.5.7 without success, there slowly appears to be some sort of pattern where the Macs seem unreliable for the operation. This is just to let you know that we are not sitting and watching but unfortunately could not pin it down yet to a particular problem in any of the system components involved.