Not that i have seen.
This seems to happen on both the CNG2 and the CGN3.
Wierd thing is... its only the WIRELESS. If it was stoping multicasting alltogether.. it would NEVER work on the units.
BUT, if you have a setup like mine.. where you have a 3rd party router set up as a wireless access point and have the wireless running through it... it WORKS 
Unfortunately.. that really only leaves those options to get it going..
Using a 3rd party router, just for the wireless as an AP.. or using the router full out, setting the modem in bridged mode.