I have WS-FTP Pro 7.0 on both multiple computers as well as the newly released IE7.

One computer has no troubles. The other gives me this interesting error when I try to start it up:

The only solution is to click ok and then kill the app from task manager.

Luckily, I found this thread in the Ipswitch forums (which also decries a lack of support from WS-FTP) where a user (who is clearly a pit-bull and chose not to give up on finding a solution - thank you Suzy!!!) has managed to find how to fix the problem, which calls for "hiding" an outdated file.

navigate to where your WSFTP is installed e.g.
c:/program files/ipswitch/ws_ftp professional
and rename PSAPI.dll to PSAPI.dll.old and then reboot

It worked. Yay.