MBMedic,
But if absolutely NOTHING happens when he turns on the ignition (no lights, power, anything), then wouldn't it be more than a starter problem? As though the entire car is not getting power?
I had the same problem with my Mercedes. The problem lingered for about 2 weeks, until I decided to tighten the wires that lead to the battery. Solved the problem instantly and problem has not occurred since.
GOod luck.

__________________
2006 E350 w/ 155k miles (Daily Driver)

Previous:
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!)