I had the same problem some months ago, i believe it was when i upgraded pcmanfm or libfm, or maybe because i stoped using gdm, consolekit and policykit, but anyway, the solution is easy, just create the /etc/filesystems
file and add the following line:
and thats all, you can add any lots of different filesystem you use if you get same problem again, here is what my /etc/filesystems looks like:
I'm pretty sure i just needed to add the ntfs-3g
lines, but added the others anyways, just because.