I have/had also the unable to connct msg#10 message... I solved the problem partly. In my case it seems it has to do with the users or drive letter. I have made seperate users on my vista computer; privat on C: and games like FSX on D: Login on private with administrator rights it seems FSUIPC installed fine on C: and the Add-0n pulldown is made visable in FSX and FSC conncteble. When I open FSX in the other user Games the Add-on remains missing!! after installing FSC as administrator No connection takes place and I get the msg#10 message. It would help to tell us in that pop up what msg#10 means to solve the problem?! Tip HAVE FSX AND FSC WORKING AS MAIN USER Re-Install the tool FSUIPC as administrator in C: from boxed CD The connection problem would be solved if the FSUIPC connects to FSX in any user/alias, after administrator acceptance, independant of the user or letter C: and D: Thanks Volker and Sascha for this great FS-tool and react if this solves this serious FSC installation problem.