It sounds exactly like that. Perhaps you ran firefox as root at some point?
I'd say:
- delete the cache:
rm -rf .cache/mozilla
- set yourself as the owner of everything under
~/.mozilla
:
chown -Rc $(id -u):$(id -g) ~/.mozilla
- make sure you can write to everything under
/.mozilla
:
chmod -Rc u+w ~/.mozilla
If you get permissions errors, run them with sudo.
How are you decoding the H.264 MVC video?