The /Console switch will soon be a thing of the past (starting with RDC 6.1) due to enhanced security. This is applicable to:
Windows Server 2008
Windows Vista Service Pack 1 (SP1) Beta and RC
Windows XP Service Pack 3 (SP3) Beta and RC.

Here is one link with additional information:

http://blogs.technet.com/askperf/archive/2008/01/04/mstsc-exe-no-more-console-switch-in-rdc-6-1.aspx