I had the exact same problem with The Last Samurai blu ray disc in my PS3 40 gig ver. 2.2 firmware... couldn't get it to work, so I sent it back to blockbuster and had them send me the HD DVD version, which worked fine and had a Dolby Digital + sound track, where the Blu Ray version I believe only has the standard dolby digital track. However I will note that the DD+ track on the HD DVD was very low, I had to turn my receiver up 10db more than normal to get to my usual listening level.
This has been the first and only disc so far to have that problem, hopefully it will be the last. I'm just glad it didn't happen to a disc that I purchased.