I decode all my videos in AVI format and by changing the
video = mplayer and general = mplayer setteings
to = oms it messes up the youtube plugin.

The work around for this if you are finding the same problem is to leave both of them as mplayer and then under
Media section at the top add the line

"avi = oms"

works like a charm, allowing it to use default for avi and mplayer for youtube.