Cannot connect to a Sun server using xterm

[a12]

Hello X users,

I access a Sun server using:
XWin.exe -query <sun-host>
I login, and start an application in the Sun server correctly.

When I start xterm using startxwin.bat, and then I start xterm to a Sun 
server using:
xterm -e /bin/telnet <sun-host> &
I get a new xterm window from the Sun server, and I login to the Sun 
server correctly.
Then I start a graphical application in the Sun server, and I get the 
following error:
*** OI_init: Error, cannot connect to X server
ntc: couldn't open a connection to a X server

What have I missed ?

Regards,

Marek