Windows 7: Microsoft expression encoder 4 screen capture stops recording randomly

I have this really stupid and endlessly frustrating problem with EE4SC. when I set it to record my full-screen I do all of my stuff that I want to be recorded(this usually takes between 30 and 40 minutes) and when I am done I press 'Shift + Ctrl + F12' to stop recording and I do hear the sound that the recording is done however when I go to preview the recording the clip is only a few minutes and everything else is missing as if I had never recorded it

I don't understand why this is because the I am running service pack 2 of screen capture and I know this error is not because of the trial version because that would at least allow me a definite 10 minutes of recording. I have looked every were on the internet And I haven't heard of anyone with this exact problem

I am running a windows 7 home premium 64Bit English and I have 4GB RAM(3.68 usable)
my processor is an Intel CORE i5-450M and my graphics card is an ATI Mobility Radeon

any help will be appreciated