FS9 hangs up

I have lately added some scenery to FS9 and after doing so attempted to start the sim. Everything loads properly with the selected aircraft and airport. However, after starting the aircraft's engine, needle movements on the instrument panel become jerky. External views disclose only a grey aircraft, and the view freezes in whatever position it is in. After using ctrl-alt-del to shut down the sim, the error msg says the following: SZ Mod Name: hungapp. appcompat.txt/fs9exe.mdmp.I am thinking there is some problem with either my graphic or sound settings, or driver. I've gone to the "Adventure Unlimited" site and looked up "hungapp" fixes, and tried removing the files suggested. This has no effect. The problem started at the stock FS9 Birmingham, AL airport, and now applies wherever I am in the world. Either there is something in the scenery files for Birmingham, AL that is upsetting the system, and is copied elsewhere in scenery around the world, or I am having problems with system resources.The sim is on a 2TB drive, which is a separate drive devoted solely to FS9 and anything having to do with it. Here is a system profile:MS Windows XP Professional 2002 SP3AMD Athlon 64 Processor 3000+1.81 GHz, 2.00 GB RAM P.S. I've tried deleting some scenery files and this seems to help - the aircraft's engines can now be started, no jerky needles, and it can be taxied for a while until the scenery moves jerkily, then everything freezes - prior to this, speech w/ATC starts to stutter.