Just to try out of curiosity, do a "power cycle" of the router- unplug it for about 30 seconds or so and them plug it in again. Sometimes this helps finalize setting changes.
Other than that i would suggest rechecking the DMZ settings to make sure the IP address matches what you gave the PS3 as well as check the PS3's settings itself (maybe enter in the DNS server numbers on there if you haven't yet along with the router IP address).
Finally, just to make sure the ports are opening for the mic go into the router's port forwarding and open UDP 6000 to 7000, 10050 and 50000.