I am actually using ActiveSkyX, as a matter of fact.

Rick.50cal: Even if I set the AP to 2000 feet or so, or adjust my fuel-air mixture perfectly (or using automixture) I have the same problem. I'm wondering if maybe it's a problem with the X-52 or something.

ETA (actually this isn't edited because I haven't even posted yet!): The autopilot did the same thing in FS9, but then started working. Blah. I think I'm just going to try and reinstall the whole shebang.