Vista - photo gallery video thumbnail problems

Hi,
i have windows vista ultimate 32bit.

Some of my videos don't display thumbnail in photo gallery. It is not a
problem with my files, because similar files (same extention, same source)
are displayed correctly when others are not. I see no reason for this, I
suspect it is a bug.

It happens with all types of video: avi, mpeg, mpg.... and seems totally
random.

Is there a way to force generation on specific videos ? (not ALL of them
since I have many).

Will this be fixed in a future version ?

I found an easy workaround:

Create a folder outside of your image gallery structure, like on your
desktop. Set it to display the largest possible thumb. Then MOVE (do not
copy) your video with no thumbs here.

You will see that the thumbnail are correctly generated. Then move them back
in your photo gallery. Done !

Well it doesn't seem that easy in fact: in some cases it will simply not work
:/ .