Default FS9 problem. A/c moving - parking brake set, engine off etc

Hi,I've always had this problem within my FS, even before addons were added, that a/c with parking brake set, engines off, no wind, is gradually moving VERY slowly forward. Within about 10 mins, the a/c is totally out of it's parking bay and into the terminal.Is there any fix for this?Previous versions of FS never had this problem.Cheershttp://forums.avsim.net/user_files/67960.jpghttp://www.onlinesimulationsolutions.com/Athlon 64 3000, 19dba Zalman CPU fan, MSI K8T-NEO, 1GB PC3200 DDR400, HIS Excalibur 9800 Pro 128mb, 60GB HD.Trainee Airline Pilot (Completing PPL, ATPL this year).