Its odd that 6 months ago I ran into this very topic. My 1080p movies would stutter like hell over the network but 72p would work fine. I got around this by using MK2VOB then copying over the large files to the PS3 HD. The largest file I copied to the PS3 was 35 gig and it took forever but most 10-15 gig movies aren't to bad.
After the recent FW update came out a few days ago, for shits n giggles I tried to stream a 1080p movie and it worked fine. I was shocked so i tested out other movies that previously failed and to my surprise they work! Not sure if this is due to the PS3 FW or newer version of TVersity.