I've noticed that my SimConnect.xml file prevents FSUIPC from loading and hence I have no Add On menu in FSX. I had been using SimConnect.xml & SimConnect.ini etc to run a 3rd party program on my client machine (which it DID without any problem at all) but decided that installing the 3rd party prog onto my Vista machine (server) was the only way I could retain the Add on menu and FSUIPC and AFCAD etc. My two PCs are networked using a Netgear DG835 Firewall router. The only 'issue' I had in configuring the SimConnect.xml file and the SimConnect.cfg file was the 'port' entry. As both machines have WIndows Firewall turned off I tried leaving the port entry blank but got no connection - so I chose Port 500 and bingo SimConnect worked OK. Anyway, if anyone has any idea as to why SimConnect.xml causes this I'd appreciate knowing. btw I deleted the original SimConnect.dll file from the C:\WINDOWS\WinSxS directory and used the FSX repair option to ensure that it wasn't corrupt in any way. SP1 is of course installed as well. Also my Anti virus program is turned off. I'm now convinced - having 'troubled' Pete Dowson on his forum, that it's not a FSUIPC problem at all, but a SimConnect one. This is very similar to the problem in this post: http://www.fsdeveloper.com/forum/showthread.php?t=3302 Thanks.