One problem related to brake light on has been reported for the 2008 BMW 528. The most recently reported issues are listed below.
Rear exterior lights(brake, tail, & turn signal) - melted wire assembly is causing malfunction. While driving I noticed a "burning" smell. Shortly thereafter, all at once my dash indicated that my passenger side tail light, brake light, and turn signal had simultaneously malfunctioned. The wiring harness that attaches to the light assembly is melted. BMW did a recall of over 2,500 3-series vehicles for the exact same issue but has not recalled the 5-series (????) this is a safety issue that needs to be addressed.