avid media composer 6.5 freezing source screen

[debojam]

hi
my name is dvora i'm new here
and i really like this forum
i have a big problem
the source screen where i display my files is freezing
meaning a few things,
it display the audio but not the video video is frozen while the sound isnt
but its not this way all the time but very often and nothing special i do to make this happening

so i have avid media composer 6.5
16gb of ram
intel xeoon
cpu e5520 2 processor 2.26ghz 2.27ghz
graphics card nvidia quadro fx 4500

thank you in advance for the help
dvora