% echo "*background: stupid-broken-desktop-setting" | xrdb -merge
% wish
Application initialization failed: this isn't a Tk applicationunknown color name "stupid-broken-desktop-setting"
Apparently many linux desktop systems try to set xrdb entries to make old applications look a little more like other desktop applications (details on this are thin, and of course vary between different desktops). Unfortunately, some of the time this makes all wish applications break.
While the true blame lies at the feet of these desktop environments, it would be nice if Tk was robust in the face of this type of problem.