I had the passenger side hood latch get stuck on my '99 E300 W210. No matter how hard I pulled on the release cable, the latch would not release and pop up. I had no problem with the driver side latch, which poped up normally.

I though I was going to be forced to break through the headlight to get to the hood latch. Then I found a nice solution.

I released the latch on the driver's side, and pulled the hood up (about 1/2 inch)and put some wood shims to hold the hood up. The wood shims between the top of the bumper and hood held it open very slightly. Then I was able to get a 12" metal hack saw blade between the top of the small headlight and the lip of the hood. I was just able to reach the latch pin with the blade, and slowly sawed through the 3/16" diameter pin. I could get about a 1 inch stroke with the blade, just enough. After about a 1/2 hour, i sawed through the pin, and opened the hood. Never thought I would be so happy to see my engine again!