This is a known issue. There are a multitude of forum posts about this. Perform a forum search. That being said, I experience this issue as well. I've experienced it since moving from Windows XP to Windows 7. I use a laptop in conjunction with an external keyboard and mouse. I'm running PEP v1.1.20 and Windows 7 Professional 64-bit. With my external keyboard and mouse connected I get the error. If they're not connected I don't get the error. No issues downloading (Ctrl+D) to my TSU9600's so long as I disconnect my external keyboard and mouse first.