The temperature hit 4 below this morning at Lake Tahoe. When I started my '05 FEH, the ABS and brake warning lights came on, along with a message to "check brake system." To make a long story short, apparantly the regenerative braking system was not working. The hybrid power display showed no green arrows flowing to the battery when brakes were applied, although I could stop. I drove about six miles with this condition, then parked in the sun. Three hours later, with the temperature in the mid 20's, I restarted the vehicle. All systems were normal. The power display showed a flow to the battery while braking. Has anyone else had this problem, and what is there about the braking system that could cause a temporary failure of regenerative braking in very cold weather? Thanks for your help.