You might remember the "Vaulty/Tubemate" conflict saga, of a little while back.
I got rid of "Vaulty" ( a Gallery secret vault), and Tubemate at the time and their files, using a file manager. That solved the problem of any "Tubemate" YouTube downloads and even movies downloaded from a PC ending up with a thumbnail Gallery photo of a video in ''Vaulty".
Later I re-installed Tubemate, and didn't seem to have any problems, - until today. I opened Tubmate, and it offered an updated version, which I accepted.
I used it to download a Citroen C6 car review from the Fifth Gear TV show.
It added a new widget to the Gallery, "Movies" - which I hadn't seen before, which was fine, but it also add a thumbnail of a Youtube dog video of some bulldogs bouncing on a trampoline, I downloaded and
deleted, yesterday. So, in effect the Citroen video could be accessed from "Movies" in Gallery, and also there as on the SD card with the bulldog thumbnail.
Now surely, it must have been "Tubemate" (the update now) and probably before (previous issues) that caused Vaulty problems.
I used my two File Manager apps to investigate and found some "Folder" called "DCIM" which contained thumbnails of photos and videos in Gallery, including the bulldog video. I deleted it, and anything I could find dated yesterday.
* I think these items were in the main "Backup" folder.
Also came across some "software" from some company "Speed Software" dated yesterday. As I didn't download any apps. yesterday, I deleted it too, whatever it was.
It seems you may only think you are deleting things, but they may also have automatically backed up and the backup isn't deleted as well. But don't take that as Gospel.
So, as my new thumbnail in Gallery problem started the same day as I accepted the "Tubemate" update, - I suggest Tubemate may cause these problems.
** I have just run a test of a Youtube download taken via PC of a remarkable parrot in Japan that can undo ring puzzles in 5 seconds and speaks Japanese (how clever is that!). And I'm glad to say that in Gallery when downloaded to the Streak, it didn't come up with a thumbnail of 2 bulldogs bouncing on a trampoline, but a
Macaw parrot. And the thumbnail of the bulldogs that was there has
gone. So, whatever files I deleted with the File Manager must have worked.
The closes up of the Macaw, and the whole video has stunning resolution! A real head turner!
But I am a bit hesitant to use "Tubemate" again.