I barely use the Media Player that came with the N900 so I can't say when this started but I have my videos stored in MyDocs/.videos and they are .mp4 format and .flv format however the .flv ones no longer show up in media player. They do work though, I tested them, just they are't listed.

I used this command in hope my database would be refreshed and it was but still no .flv files listed.
tacker-processes -r

Can any one offer a solution?
Thank You

SOLUTION
Get rooted > sudo gainroot
Exter Command > update-tracker-ontology -c Videos -a video/x-flv