I think I have a lead. It was the AC
I (used to) do that trick with the MY00 where you press the two buttons on the AC unit to bring up the diagnostic mode (so I can check my engine temp and know exactly when it's warmed up). Problem is, because one of the buttons is the upper vent switch, occasionally the AC would switch to upper vent. The problem is when cold, moist air would come thru and apparently moisten up that vinyl. I guess I just didn't really notice where the air was coming from, I don't run the AC that hard (sometimes it would be just a tiny bit at night when the air is damp), and damn...it musta taken its toll.
So here's a lesson for all those new owners out there, careful with air going thru the UPPER VENT. It's it's moist, it might do some damage to the dash!
-David