can not start X as non-root user

["[loonyx | rolf joho]" <loonyx@gmx.net>]

hi there
i just set up a new woody-box with xfree 4.1 and gnome 1.4*.
gdm runs fine and i can login there or running startx X as root. 
however, if i try to log in through gdm or running startx as a normal 
user, i can not run X and fall back to gdm or to the console respectively.
if i have a look at my /var/log/XF there are entries like those:

(EE) xf86OpenSerial: Cannot open device /dev/input/mice
        No such device.
(EE) Generic Mouse: cannot open input device
(EE) PreInit filed for input device "Generic Mouse"

but, if there is really something wrong with my mouse-setup, why can i 
login fine as root?

thanks for help

rolf


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