The solution to this one is extremely stupid, but nowhere near as heinous as the Valve tools fix...
Windows Key+Fto bring up the Search Results window.
2) Select "
3) Select "
Without an animated screen character".
For some reason, the animated search dog in the Search Results window causes the right-click menu in Radiant to not be able to show up.
Also, this is the Missing Post...in other words, this is my 404th blog entry.
Given that I never expected to hit 100, hitting 404 is quite an accomplishment.