Any DMCA complaint based on a widely-known Windows feature seems like a longshot, so SunnComm seems to be zeroing in on the fact that Halderman named a specific driver installed by MediaMax CD3 ("SbcpHid") that should be deleted to un-cripple your CD drive. Halderman violated the DMCA by telling people about this (pretty obvious) remedy, according to SunnComm.
This is one of the signal stupidities of the DMCA's anti-research provisions: their real effect is to attack speech as a way of communicating knowledge. When communication is attacked, innovation and the market suffers.
Halderman could have sucessfully recovered his system from the damage inflicted by a SunnComm-infected audio disc and no one would have known, or been able to prosecute him for it. It would also have allowed SunnComm to continue to misrepresent the effectiveness of their solutions to their customers. By publicizing the flaws in SunnComm's technology, Halderman will ultimately make efforts by similar companies stronger. I'm not keen to see music locked up on plastic and aluminum, but I'm less keen on seeing crap technology protected by crap legislation.
