Here is a possible fix for the flashing Bridge Messages/Bridge Locked repeated password prompt problem without wiping.
1. Close Bridge Messages, if open.
2. Go into the Date & Time settings on the PB.
3. Set the date either forward or back several years.
4. Open Bridge Messages, enter password if needed, and see if Messages works normally.
5. If Bridge Messages does not work, repeat all the above but with a farther out date.
6. If Bridge Messages does work, leave Bridge Messages open and go back to Date & Time settings. Set to the correct date.
7. Disconnect (not Lock) the Bridge.
8. Tap on Bridge Messages, re-enter Password if needed, and see if Bridge Messages works normally.
I did the above and Bridge Messages is now working for me, with the correct date set, even after closing and re-opening Messages, all without wiping my Playbook.
Some background on what happened to me: After I received the .688 update and restarted my PB, I used it for a bit and turned it off. When I turned it back on and tried to use Bridge Messages, I received the repeated prompts saying bridge was locked. It didn't matter that I would enter the correct password, I kept getting the same prompt. Disabling the password on the phone didn't matter. I could not access Messages through Bridge. I could access all the other Bridge apps.
I tried everything. Pairing, unpairing, repairing (Ha!), changing the password, uninstalling and reinstalling the bridge on the phone, and deleting recent messages. Nothing worked. I did not want to wipe, been down that path and hate it. I found the solution on the Forums for accessing them by using address
http://localhost:187/messages/ in the browser for a bit. I didn't realize that the Bridge sessions were separate instances of the browser. Eventually, I started having the same problem with that, too. I found that doing a Clear All under Privacy & Settings in the browser resolved the problem. That got me to thinking that there was some kind of corruption in the browser caching for Bridge Messages on the PB. Unfortunately you can't access browser settings in the Bridge Apps to clear them. I wondered if whatever it was would eventually clear out/expire based on date. I started changing the date on the PB and opening/closing Bridge Messages. I found that if I set the date to August, 1, 2012, Bridge Messages would work normally. If I closed the app, set the date to August 2, and reopened, it wouldn't work. I also found that if I set the date several years into the future, it worked. As long as I kept the app open, even if I set the date back to the correct date, messages would work. However, if I closed and reopned it while at the correct date, it would no longer work. I don't know much about how browsers work so I don't know that my theory is correct. I just know the steps above fixed the problem for me.
I'd be interested in hearing if this works for others having the same problem.