Magix technical support would definitely be better suited to advise concerning this kind of problem and provide some tips for burn troubleshooting that apply to your particular case.
You should snoop around a bit to make sure you have the correct file for your system (sometimes they have more than one available). Magix provides these burn routines periodically. Basically, if you have another program which burns DVDs (Roxio caused me problems) you can create a conflict. I was always able to get MEP burning again by installing the latest Magix Burn Routine (and most of the time rebooting).