Alright, no one has objected and it's late night so....
Decided to do a disk cleanup on my ancient laptop running XP (FF 45.0.2) over the weekend, and that went fine. Then thought maybe I should defragment my C drive, and that went fine too (albeit both took about 3 hours total). My laptop was running so much faster and more smoothly afterward, and I was looking forward to a MUCH better working environment this morning. And then I woke up and logged in to my MTurk account.
Immediately saw a message in bright red under the HDB menu stating an "unknown error" occurred that was not directly related to HDB and the error matched no other error message. So I:
1. Tried and failed to update HDB
2. Tried and failed to import HDB backup
3. Checked for HDB updates (none more recent than my installed version)
4. Checked for Greasemonkey updates (")
5. Checked for updates of other extensions
6. Found and installed updates for TO (Kadauchi version) and HIT Scraper
7. Re-enabled HDB and tried to access MTurk dashboard and received original "unknown error" message
8. Checked every forum imaginable for solutions
9. Made sure my FF History settings were not set to 'private' or 'never remember history'
10. Cleared cookies, etc. and removed HDB
11. Disabled all other Greasemonkey extensions and Greasemonkey itself
12. Reinstalled GM and HDB and got the same error message.
13. Went outside and walked around the block twice in lieu of tossing my computer against a wall.
14. Cleared cookies, cache, etc. again
15. Disabled GM and HDB again
16. Did a system restore to the time before I did the disk cleanup and defragmentation
17. Reinstalled GM and HDB again and got the same unknown error message
18. Searched Google for ways to completely uninstall FF
19. Decided to try to refresh FF
20. Removed all cookies, history, etc. prior to refreshing FF
21. Refreshed FF, reinstalled GM and HDB
22. *******!!!!!!!!!!!!!WORKED!!!!!!!!!!!!!!!!!!**********
23. No longer received HDB error message. Updated database and imported backup. Working perfectly
24. Installed most recently updated versions of TO (Kadauchi), TM, and HS but did not install any other GM US for now.
After 6 hours, everything is working beautifully and my computer/internet is running faster than ever.
*Commencing drinking now.*