I might have a thorough dislike for Firefox now. Before I updates, I could find the cache and locate a youtube video, name it to .AVI extension and play it without being on the net.
I could refresh that cache directory as I downloaded, ensuring the youtube vid was being saved to disk. Now, the file DELETES itself after it finishes downloading.
How dare those bastards delete a file I just downloaded, FFS. Or maybe this is youtube, I dunno. But it happened after I updated FireFox.
EDIT: Yes, I use AdBlock as well. Very, very good.