AAAAAAAArrrrrrrrrrrrgggggggghhhhhhhhhhhh!!!!!! Windows 7 did another update - problem is back. System restore point fails. I will look for a different USB/SER unit and try that next....

Had a minor crash in window 7. Trying to do a restore point seemed to activate the automatic update. Problem seems to have disappeared entirely! 190k bytes send and received (so far) at 19.2 k baud with zero errors. Thanks for the help.

It is using a Prolific USB to serial adapter. The same adapter works fine on 2 other computers running 32 bit XP instead of 64 bit windows 7. Turning off the FIFO (assuming that is actually happening) seems to have no effect. This problem is erratic. A DOS terminal program running a loopback test …

I use a terminal program to access various external devices. Everything works fine under XP on two other computers, but my new Windows 7 machine starts returning input data 'one late' after a lot of data has come in. This condition can only be cleared by exiting DosBox and restarting it. serial1= …