I picked up a fresh N9 64GB (made in Finland) a few weeks ago, running 005/Asia firmware (PR 1.1, IIRC) out of the box, and I didn't think to flash it to 001/ROW firmware before I ran the PR 1.3 update OTA.

Funny thing, I hadn't run into this 'forgotten credentials' issue with my previous N9 (made in China), but my experience fixing this issue on my 'new' (Finland) N9 was the following...

Apologies for not giving appropriate credit, but I tried one of jalyst's suggestions in the bugzilla thread...

1. delete all accounts
2. reset device (settings -> reset, etc...)
3. recreate accounts
4. reboot to verify issue is resolved, i.e. N9 doesn't nag for credentials again.

This didn't happen to work for me, so I repeated the steps above, and the issue seems to be fixed now.

One more interesting bit of trivia is that I found that the first reset didn't seem to wipe out all apps/data, most notably the Vimeo and Meecast apps.

After a second reset, Vimeo and Meecast were gone.

I had actually also tried to reflash from the 005/Asia firmware to 001/ROW firmware, but of course that resulted in 'downgrade not possible' flasher complaints.