/etc/csh.cshrc in prior releases has been changed to /etc/csh.login. tcsh DOES NOT use this file, and thus the prompt never gets set, or all of the other winderfull things that /etc/csh.cshrc normally did. renaming /etc/csh.login to /etc/csh.cshrc restored normal behavior to tcsh. I did NOT test the behavior with csh, nor did I check if tcsh and csh were the same program. (one sym-linked to the other)
tcsh invokes csh.login OK for login shells here. In setup-2.0.6-1, which will be in the next Raw Hide release, functionality will be split between csh.login & csh.cshrc in a manner similar to /etc/bashrc & /etc/profile.