I have seen this before. When I install QTP 11 then attempted to roll back to QTP 10. The only way I could fix this issue is to do a clean uninstall of QTP and the installed QTP again. Recommend reviewing HP documents
Document ID: [link text][1]
Title: How to perform a clean uninstall of QuickTest Professional (QTP)?
Document ID: [KM822411 http://support.openview.hp.com/selfsolve/document/KM822411][2]
Title: How to perform a clean uninstall of QuickTest Add-in For Quality Center
Document ID: [KM1016043 http://support.openview.hp.com/selfsolve/document/KM1016043][3]
Title: How to perform a Clean Uninstallof Service Test?
[1]: http://support.openview.hp.com/selfsolve/document/KM171368
[2]: http://support.openview.hp.com/selfsolve/document/KM822411
[3]: http://support.openview.hp.com/selfsolve/document/KM1016043