Stock RH 6.1, XF86_SVGA server, gdm, as root (just to make sure it wasn't perms) from a text screen, startx -- :{1,2,3} all work fine, starting up an X server on vt's {8,9,10} respectively. doing the startx -- :4 to start a fifth server, the screen blanks like it's starting X, then it dies and kicks back to the text vt, with the messages: failed to set default font path 'unix/:-1' Fatal server error: could not open default font 'fixed' Out of curiosity, I stop'd and start'd xfs and then :4 worked fine (this will probably break fonts on :{0,1,2,3} though :) I can't find anything in the xfs docs about a limitation to four X servers, so I'm unsure of how to fix this. This is on a user's machine (board designer) and he claims that the capability to start 6 X sessions worked fine in RH 6.0 and only after the 6.1 reinstall (fresh install, no upgrade) did it fail.
in /etc/X11/fs/config, change the line client-limit = 4 with the number of X Sessions you want to have simultneously.
or change clone-self=off to clone-self=on. This will be the new default in 6.2.