Thank's Pete.
It was not my intention to give anyone the impression that i thought it had to be FSUIPC, but i felt i had to ask you too in my investigation of what it can be, as it's a complete mystery to me. Thinking about it, i should have figured out Jeppesens weather don't use FSUIPC, but i'm not that much of an expert...
But you've given me a couple of ideas i'll go on with. Could be interesting to see what will happen if i enter a certain force of wind. I also look into the other thing. Corruption could be a possible reason, as i haven't touched any settings pryor to the occurance of the problem - except installing FS9.1.
It's of course easier to take off and land when there's no wind, but not very realistic... :D
Thank's again, Pete for taking your time and have a nice weekend!