I believe this issue does not happen in latest versions of pcmanfm. And if it does then it might be issue with your MIME database. In any case the version 0.9.10-3 is pretty much outdated and unsupported. I would ask you to install newer version. Since you are using Debian stable, add the wheezy-backports repository and install newer pcmanfm using it, please. Then test if issue still happens and add your info into the report.
-- To UNSUBSCRIBE, email to debian-bugs-dist-requ...@lists.debian.org with a subject of "unsubscribe". Trouble? Contact listmas...@lists.debian.org