Does it mean you use it from a USB stick, or did you create a portable.txt inside the program folder? A portable version does not use the registry for file associations, so this may lead into several problems and you should use File=>Open from the programs to open a file, not a double click.
At first I was using it from USB stick, but it turned out to be very useful so I copied the program folder to my hard drive. I know the portable version doesn't use registry entries for file associations (IIRC version 2010 didn't even had an option to register file types), so I added them manually with Explorer (Tools -> Directory Options -> File types ...or something similar, I use non-english Windows). It worked perfectly with SoftMaker Office 2010 - that's why I have so many odt files even though I rarely use LibreOffice. But now I have this problem