That makes sense.
Anyway, I didn't have any cache data to clear, but with sync turned off, I cleared out the app data, and now everything seems to be back in working order. I guess leaving sync enabled on the last few clearing attempts kept something ugly from being deleted.
You have saved me from a trip to Verizon, (at least until I try in vain to sweet talk them into letting me pick up a Galaxy Nexus or Droid RAZR at a reasonable off-contract price [lol]).
Thanks a lot!