The problem is solved. The problem was because of the configuration files which I didn't delete after I had built gmplayer from source and uninstalled. When I built it from source, I had to choose a ttf font in a directory the X Window system will search for font. But the font I had chosen to be the target of ~/.mplayer/subfont.ttf was not in one among those directories.
Thought this might be useful for other users who might face the same problem:
To add a font directory to be searched by x window system edit the following file:
/etc/X11/xfs/config or
/etc/X11/fs/config (fc5)
search for the line beginning with "catalogue =" and add the directory to the list.
When you are building from source when you make the symbolic link
~/.mplayer/subfont.ttf , make sure the target is in one of the directories searched by the XWindowsystem for fonts!
I took some of the information from
http://www.linux.org.mt/node/51#N10057