I have several machines wired via Ethernet directly to my MI424WR-GEN2 (PS3, TV, FIOS DVR, etc.)
I also have several machines connecting wirelessly to the same router (PCs, iPad, etc.).
This setup has always worked great! However, recently it seems as if the wired objects exist on a totally different network from the wireless objects.
For example, I use my PS3 to stream video to my TV. Usually, it detects multiple PCs running WMP and my main PC running PSM.
Since this problem has started occuring, though, the PS3 doesn't detect anything unless I disconnect the PS3 from the Ethernet connection and switch it to wireless, in which case it detects all of the wireless PCs.
If I try connecting a PC directly to the router, the PS3 will only detect it if the PS3 itself is also connected via Ethernet.
Login to the router, Advanced -> Yes -> IPMG Proxy - Set IGMP Proxy (Enable/Disable): to Disable and save.