I have started and read several threads due to my K1200GT "brake failure" light coming on and staying on. Heard lots of horror stories about $1,800+ bills from BMW to replace the ABS module. I think this applies to all ABSII modules but definitely the 2008.
Here is the problem. Bad brushes in the ABS pump motor. This was told to me by the guy at ModuleMasters.com, check them out online (Tech's name is Tyler).
Sent mine to him after long investigation, and trips to the shop with no success and he just called me to say "sure enough had a stuck brush in the motor". Repair + warranty $150.00!
I have a GS911 code reader and you always get a couple of codes both similar to "low voltage to ABS pump supply... error". The real issue is swollen, cracked, or just stuck brushes in the motor.
The module itself is made BMW style (all embossed together so no internal access). These guys have played around with old units and found a way to affect the repair. For my money it was worth it to have them do it and not take a chance to ruin mine doing it myself blind (drill into the wrong spot and uh-oh!!)
Hope this helps out all of you in the same position. These guys are good, got my unit wednesday this week and called with diagnosis Friday.
I hope to get the module back next week, bleed the brakes and be off and running again.