The OVP is the Overvolt Protection Relay. It protects the system (car's computer, etc.) from getting fried. Many of them were faulty from the start. My car (1995 C280) had the same symptoms as yours... it would stall at stop lights, while turning etc. But my car would also have a tough time starting when the engine was warm. For example, I would drive somewhere, shut engine off, and then try and restart the engine, and it wouldn't start. It would turn, but it wouldn't fire. Well I replaced the OVP and the car has never not started, and has not stalled on me since. Another possible culprit for this type of behavior could be the fuel pump relay, also a common failure.
The overvolt protection relay is under the hood to the rear on the passenger side (I think that's where yours should too, I could be wrong though.). It can have either one or two fuses on top of it, and it should be silver (or red!?). I don't know the part number off hand, but I'm sure someone else can help you out.
Cost for replacement is about $50. I got mine here @ Partsshop.
This is where I would start for your stalling problem, then I'd get to the fuel pump relay, and then if that doesn't work, have it taken in or whatever.
As for your Check Engine light, I would count exactly how many times the LED flashes so that your problem can be narrowed down more!
2006 E350 w/ 155k miles (Daily Driver)
1993 300E 3.2L Sedan w/ close to about 300k miles
2003 E500 Brilliant Silver (Had 217k miles when totalled!)
1989 300E with 289,000 miles (had for <1 yr while in HI)
03 CLK 500 cabrio (Mom's)
2006 C230k (Dad's)
1999 S420 (Mom's/Dad's)
2000 C230k Sport sedans
2001 CLK320 Cabrio (Mom's)
1995 C280 My First Mercedes-Benz... (155k miles. EXCEPTIONAL AUTOMOBILE. Was Very hard to let go of!)