Format Factory does not recognize the source file size

Hi, I've beeen having a problem when trying to convert movies with Format Factory.
Sometimes the source file (usually an HD movie) is not fully recognized by Format Factory.
For instance, the source file is 7.9Gb, but when I select it and add it to the conversion queue, Format Factory only reads 4Gb. Or when a file is 1.9Gb, FF only reads 300Mb. What could be the problem? I've tried emailing the support email they offer but have had no answer... I really love Format Factory and prefer it over all other free converters out there, but this is really annoying!

I'm attaching a couple of screens in case my explanation is not clear. This is the exact same video file but on Format Factory it shows 381Mb and on Windows Explorer it is 4.37Gb.

I'm using Win7 and FF V2.7, and have Klite codec pack installed.
Any help would be highly appreciated!