[xfce] Xming with putty

Hi,

I was connecting to a ubuntu server using xming and putty. I have installed ubuntu desktop in remote machine. But suddenly when I tried once, I could not get the desktop and error is as follows,

X: user not authorized to run the x server, aborting.
No protocol specified.
No protocol specified.
xint: giving up
xint: unable to connect to x server: Resource temporarily unavailable.
xint: server error.

What am I supposed to do?

Regards