Two problems related to car stall have been reported for the 2008 BMW 5 Series. The most recently reported issues are listed below.
I purchased a certified, pre-owned 2008 BMW 535xi with approx. 22,000 miles on 10/23/10. Subsequent to my purchase, I discovered the high-pressure fuel pump in the vehicle had earlier failed and been replaced. On 10/28/10, just 5 days after purchasing - I was driving on a surface street when the car began violently shaking and rocking, the engine lost substantial power and nearly stalled, and the engine malfunction indicator lit. I took the vehicle in for service on 10/28/10 and the vehicle was returned 10/30/10. 3 of 4 fuel injectors were replaced along with all sparkplugs. At high speeds, this type of engine malfunction would pose an extreme safety risk in my opinion. I have contacted BMW USA and the dealership where I purchased the vehicle and I have not been satisfied with the response to-date.
Car in for service for the third time. The first two times, high-pressure fuel pump was replaced. This time, 2 fuel injectors and plugs will be replaced. Symptoms have been the same each time - engine light comes on, low power message is displayed and car runs extremely rough. One incident required the vehicle to be towed to the shop as it stalled while driving and would not re-start. Based on information on this site and in the BMW forums, I am concerned that the car is not being adequately repaired, but just patched. I do not feel comfortable driving a car that might stall or lose significant power while driving in highway conditions.