HELP~ HTPC - Bluray stuttering problems

[discover]

have an XPS with a core i7 920/ ati rad hd 3600 gfx/ 9gb 1033mhz tri-channel ram and 640gb sata2 hd.
i have a monitor with the pc, but playback is on monitor 2 - a 37 sammy lcd 1080p.
software includes ffdshow av codecs and mediaplayer classic. over the past few months, playback of bluray files was absolutely perfect, i could download, burn a cd, send data through usb and more multitasking all at once without any problems. now recently i noticed, whichever bluray file i play i get this really bad lag/stutter every few minutes and the movies arent watchable anymore.
i never changed any settings on any software cant understand whats gone wrong.
anyone got any ideas what may have gone wrong?

 

[discover]

anyone?? any suggestions please?

 

[Sephiroth0000]

Are you playing via disc, ISO's?, files? What other programs do you have running at the time... antivirus scanning?, etc

 

[wolvers]

If it was fine, and now it's not, then you must of installed something or an update had occurred that is causing an issue. I can't think of any other reason...........oh, except a virus of course.