Actually i have downloaded the new FSUIPC for FSX.
After installing i had severe probs with FSX.Over at simFlight there are several people with similar expiriences.As far as i can see nobody of them has found a solution yet.

Now i have already found a solution!It might only work for those of you which also use NOD32 as Virus protection.But i´m convinced that my expirience will also work for other Virus protecting progs.

The reason for these probs(fsx just shuts down) is the fact that there is an internal "communication" between FSUIPC and FSX.This happens via "SimConnect".
And then it comes to,what it has to come to.NOD32 is doing his "work" and stops this communication.

So the solution is,just tell NOD that this communication has to be allowed.
To do so you have to open the "Imon" Module and under the menupoint "Setup"make the entry that FSX.exe has no longer to be watched.

That´s it!

It's actually a very good tip.