had problems with voip and my belkin, calls cut off, this was due to the UDP flood thing. Got round it to a point by diasbling SPi in the follwoing 'hidden' page:

http://192.168.2.1/firewall_spi_h.stm

not ideal for me though as its disabling some of the protection, and replaced by a safecom router with QoS, that the second time I've mentioned safecom on the forum - no I don't work for them ;)

nothing else seemed to work with the belkin, a call to thier tech support led nowhere. searching the web and its seems its an issue even with the current belkin models.