[CentOS] VNC server problem

hi,

	i just installed the vnc and vncserver package.
i started the server with command vncserver :2

when i connected to vncserver using vncviewer 192.168.1.101:5902 
i prompted for the password then it display i windows with a terminal

but when gui is enabled by uncommenting the two lines in .vnc/xstartup
file
i diplays a blank window when connecting from the remote vncviewer


i there any thing else to be configured

please help me