My wife has recently upgraded to Lightroom 4 and uses LR to store all the HD movies of the family.
In LR3, the default player was external to Lightroom (Windows Media Player) and this worked fine. However in LR4, it appears that quicktime is used. HD movies in quicktime are very slow and jerky but they run fine in media player.
I'm not 100% sure of the issue but it looks like something to do with hardware acceleration (i.e. quicktime is not using it but WMP does).
My wifes PC is not overly powerful (cpu is an Intel Atom D525 I think) but it obviously runs full HD movies in WMP OK so we're happy its good enough and dont have the funds to upgrade yet.
My question is: can you get LR4 to play videos in an external program (WMP) rather than trying to use the inbuilt one?