odd lag while playing 1GB+ MKV in fullscreen in 1 monitor
 

hey all
so while watching a 1.1GB hd MKV file (tried several) on on my 32inch monitor everything is fine, no lag, if i use mouse wheel to make the BSplayer window as big as the screen, still no lag. if i double click to fullscreen, bam, crazy gitter lag video only (no audio issues)

strange thing is if i do the same on my 24 inch monitor, it works fine in fullscreen..
also any other player works fine in the 32 inch while fullscreen - and i've watched 20 other 300-400MB files on the 32 incher fullscreen no problems

help?