WinSCP interrupts or kills every other connection on my pc

I apologize if this has been already posted. I searched a few times but didn't find anything either here or on the wider internet.

When I run WinSCP or PSCP, it works, albeit slowly, and it promptly kills every other connection on my PC, from AIM & Gtalk to ping and HTTP. As soon as the program is terminated or the transfer completes, everything works again. If I SFTP to the same server, no problem. If I use PSCP on another PC, no problem. It's just this pc, and just SCP. Anyone have any ideas?