I cannot login in CDE. Session almost starts and then the login screen

CDE Error displayed in a pop-up window:

DT messaging system could not be started.
To correct the problem
1- chose Ok to return to the login screen
2- select failsafe session from the login screen's option menu and login.
3- Check to see that the host name is correct in these locations
For additional information see the DT users guide.

Anypne can tell me the solution.