Error: Unknown error encoding file

Question

re: issue encoding for h264 YouTube HD system preset

Hi, i have a win server 2008, and expression encoder ultimate sp2, desktop experience, quicktime pro and media player codec pack 4.2.4 ... i will be able to encode for Xbox (smooth streaming) ...  but now i want to use also for my web streaming just regular h264 and different bit rates... 

so i started with the system preset under 'Encoding for Online Services' -> 'HD' ->  'H.264 YouTube HD' ... this is not actually all the values i want but it will be a starting point ... i actually want to set fixed Frames/sec and have multiple sizes  at different bit rates . but i have an issue just with the default preset ... it starts encoding ... and it drops in the middle and the only error is 'Error: Unknown error encoding file.' 

is there a way to get more details out of expression i knew the transcoding world was tough, but i am getting frustrated a little bit :(

thanks

Brian