The Nav system on my 2000 ML430 has begun flashing an error message: 'error reading CD-Rom'. Nav intro screen shows up but then the error appears. Mercedes wants $2,200 for a new module, without even diagnosing the problem. System worked fine up until now. Anyone else run into a similar issue? Frustrating with only 49k miles over 6 years. Would love any suggestions about how to resolve this without paying an absurd sum.