QuickLook Thumbnails Not Showing

in finder go to view menu->show view options. make sure that the box "show icon preview" is checked. you need to do it in all 4 finder views separately.

Join the club. Mine is the other way around though...no thumbnails for many movies but PDFs seems fine.
I also found that dragging an item to the desktop and back sometime forces the thumbnail to appear.
Changing icon size with the little slider also gets some of them to appear, but when you change the size back, the thumbnail disappears again!.
Finder seems pretty screwed up in SL

I also tried this (deleting the Quicklook cache) and no luck, still the same issue.
I did a clean installation and this works
However, I did again the installation and imported my USER profile in FULL via the assistant when you first configured Snow Leopard (using an FULL BACKUP copy and/or Time Machine Backup) and then problem reappears
I have reinstalled DivX, Desinstalled RealPlayer deinstalled Perian and still the same issue. I cannot see the Thumbnails or the Cover Flow of the video/movie file such MPG, MPG, AVI, WMV but it works for MP4 I have for my IPod
I finally gave up and left this last installation and I did not have the energy to migrate my data, emails, settngs, etc manually.
By the way, the upgrade from Leopard 10.5.8 towards Snow Leopard 10.6 was smooth but the performance was awful specially after installing 10.6.1. With the upgrade I had the same issue with my USER account or with any, NO THUMBSNAILs for most of my videos enough though they are played correctly in Quicktime and Quicklook....

The rest of thumails work fine
Any help????