Just to let you know, I know it isn't a Euroharmony Livery (Yet!) but I flew a flight in the PSS A320 Pro last night and had exactly the same problem, (Decending at a rate greater than 4500 fpm) although on the PSS Airbus, the FMC will automatically overide the manual decent rate if you are in Approach mode, so you have no way of combating this little problem. I know it's my own fault for flying the PSS, but I love it and enjoy using it.
cheers,
Phil
EDIT: Also on the PSS, when you raise your gear, it turns out landing lights in FS9 also landing lights will not come on until you lower your gear! d**n the PSS!