It works for me but i'm on 1.2.0 with ffdshow patch, i'll go to test on 1.2.0 SVN. I did some test on youtube (some flv has bad url but i have see sometimes this before).
Thanks
It looks like the MediaPortal Extension Installer doesn't delete the file from a previous install.
So for all updaters:
Delete the OnlineVideos.dll from MediaPortal\Plugins\Windows folder, the new one is installed in MediaPortal\Plugins\Windows\OnlineVideos.
The folder MediaPortal\Plugins\Windows should only contain the dll named OnlineVideos.MediaPortal1.dll