The last 5 or 6 flights when I bring up the Load Manager it just hangs and won't let me enter fuel or passenger load. If I click on 2/3 passengers it won't do anything, but if I then move the window it accepts the entry. Everything else on my system and with the MD-11 seems to working fine just this issue.

Try updating your display driver. You can also try minimizing FSX when using the load manager.