Hello
This is a bug in FSX if you are using Windows XP with a relatively old PC. It occours very-very rarely but sometimes it comes up, we know about 3 users who had(have) this problem. The thing is that FSX wants to verify the validity of the dll we are using to project the buildings, but before the validation could be finished it drops the process due to time limit exceed.
This could happen with every modern scenery which is using DLL like FlyTampa, FSDT, Orbx etc.
Unfortunately there is no real solution for it besides trying and trying. Shut off every other program and keep clicking on yes, FSX will restart every time, but once maybe it can finish the validation in time, after that it will never ask it again (except the scenery is re-installed, than it might come up again).
If you are familiar with the dll.xml, try to erase every other dll entry except the LHBP_objectPlacer.dll lines. It could give a little bit more time for the process.
I'm very sorry about this, but we can not give better answer.
SOme additional hint here:
http://forum.simflight.com/topic/68382-fsx-fails-to-run-after-fsuipc4-first-installed/