Windows 7: RAM usage spike after video decoding

This problem has been occuring for some time now

after a period of around 10 to 20 mins when a video file has been opened, it would happen regardless of wether the videoplayer/decoder has been closed or not, there would be an invisible process completely using all avalible memory leaving only 5% which is used by other running processes

however during this time the CPU usage is the same as idle
after 10 to 20 mins of high ram usage, it would instantly revert back to normal idle memory usage




the video player i used was kmplayer and WMC:HC with CCCP
doesnt seem to happen with VLC player, altho i havent confirmed that
unsure if it only occurs with .mkv format
does not occur on online video sources such as youtube

all processes have lowered memory usage to make room for the invisible memory hog

memory diagnostics havent shown any abnormalites

4gb ram, 2 sticks DDR3
Windows 7 x64 ultimate

Solutions to this problem is gladly appreciated
and yes i did just make an account here just to make this post ^^;;