I can connect to vncserver just fine, but if i fire up x0vncserver for some sharing, the viewer will not connect:
[me@mycomp .vnc]$ x0vncserver

Fri Mar 12 13:36:45 2010
main: XTest extension present - version 2.2
main: Listening on port 5900

Fri Mar 12 13:36:48 2010
Connections: accepted: 127.0.0.1::55425
SConnection: Client needs protocol version 3.8
SConnection: Client requests security type VncAuth(2)

Fri Mar 12 13:36:54 2010
SSecurityFactoryStandard: neither Password nor PasswordFile params set
SConnection: AuthFailureException: No password configured for VNC Auth
Connections: closed: 127.0.0.1::55425 (No password configured for VNC Auth)

use vncpasswd to create a password.

after you create the password using vncpassword you need to start x0vncserver and point it to that password file:

x0vncserver --PasswordFile=/home/user/.vnc/passwd
(or whatever path that password file is stored in)