Help External Programs will not load in Cubase

I just got Cubase 5 with my audio interface and love it so far. I acquired a few programs for guitar sounds such as Guitar Rig 5 among others from friends and free versions. These programs worked for a little while but now are giving me issues. I can choose presets by scrolling in the insert tab once I select Guitar Rig or one of the other non Cubase programs, however the programs themselves stopped opening. Cubase recognize the programs when I click plugin information they show up in the list and are active. The programs themselves just will not load their window so I can work in them. Im thinking its a problem with Cubase and not the program because it seems to be every non Cubase program. I saw this issue floating around the internet in other places but it was never resolved. Please help!

An update to my issue… If i click the inserts tab and put guitar rig 5 in the top slot it wont work like i previously stated was my issue, but I just found out when I open a second spot in the inserts tab and put guitar rig 5 in the slot then the program comes up. BTW Im running Windows XP Cubase LE 5.