< -Every time I click the mouse while downloading, it causes an average of 2 re-transmits in the file download window (even if I just click on that window). Suffice it to say that more complicated things (like switching to another application) have more drastic effects. >
This sounds like your mac's serial buffer is overflowing ( hardware overrun ). On a TCP connection, this is a problem to solve in the PPP setup.
< With my old Duo250 and an old version of TF I could even unstuff files while downloading and TF would usually not skip a beat >
Of course this is how it should work. Have you tried TF 5.1.1 ( the current release version ) on your new computer?
