I Just read the blog of Rex Tang where i found out that you can't use /console anymore with the Remote Desktop client after upgrading to version 6.1. This is one of these occasions when I don't understand some descicions made at Microsoft.
But luckily the functionality isn't gone, it is just a change to a different command /admin
to read more about it look at the following post on Rex his blog.
http://blogs.msdn.com/rextang/archive/2008/02/27/7917239.aspx