EDIT: This problem has been solved. Thanks for your help.
I am trying to edit my gmplayer config file, but every time I set 'msglevel' it complains about a missing parameter. Here is what I have:
In my ~/.mplayer/config file:
Now, if I use the option -msglevel all=0 from command line to invoke gmplayer, it works just fine... Any help would be appreciated.