gdm 1.0.0 / multiple displays?

[John W Earl <jwe21 cam ac uk>]

I'm trying to run my X and Xvnc servers simultaneously on displays :0
and:1 respectively. However gdm (v.1.0.0, from the redhat 6 rpm) only
seems willing to start one display's server. In the configuration file
gdm.conf I write:

...
[servers]
0=/usr/bin/X11/X
1=/usr/bin/Xvnc:1
...

and gdm chooses to start only the latter. If I take comment out the
line 1=... then X starts up just fine. I looked around briefly and
didn't find recent source to check, so I've switched to xdm for the
time being. Anyone seen this problem/have a fix?

John