X can get its fonts from a font server, such as xfs, or by finding them directly. The 'unix/:7100' entry is telling it to use a font server listening on port 7100, and apparently it's not running or is running on a different port. As a result of this, the X server can't find the necessary fixed font.
There are two solutions to this:
1. Add a line in your X config file in the "Files" Section that directly specifies where the font can be found, like this:
(Changing it as appropriate)
2. Fix the font server. The default now is to listen on unix sockets, not TCP ports, so maybe changing the entry in the config file to be like this would help:
(Re)starting the font server may also be necessary, but without knowing more about what distro you're using I can't give you specific directions on how to do that.