There's nothing on Foxit forums.
I'd say do the following to test:
1. In Windowblinds config, switch your skin to default aero and unload Windowblinds.
2. Reboot.
3. Reopen Foxit and see if the problem still exists.
If that solves the problem, then exclude Foxit from Windowblinds in the "Per application" tab of Settings.