I've noticed that the A750 is "fussier" about what it will play via uPnP (DLNA) streaming than it is for playback via Infolink (USB). I have content that will play just fine if I put it on a FAT32 mass storage device and plug it into the TV, but will NOT play (Unsupported file type) if streamed via uPnP.
It would be nice if the TV weren't so fussy about streaming vs. USB.

Chowhound
Comic Vine
GameFAQs
GameSpot
Giant Bomb
TechRepublic