I've had this happen once before and it just happened again:
I delete a large avi file (600+ mb) off the mmc2 and it doesnt free up the memory that it held.
Looking in the control panel a very similar size is now categorized as 'other files'.
I deleted using emelfm2.

Any ideas?

I even tried restarting the tablet.

Is the avi file read-only?

i was testing dvd playback on the n810 and i had an old ripped movie in avi format that i just loaded onto it.
it played vert well and i had no trouble deleting it using emelfm2 - so i cant actually see it anywhere.
not quite sure what to do to reclaim that diskspace as the int mem card still think its occupying it.
is there...a trashcan i need to empty?

have you rebooted since?

In Linux, a file isn't really deleted as long as any application has the file open (Windows just gives you an error if you attempt to delete an open file). You can check to see if the movie player process is still running and kill it. You can also try rebooting.