On both Windows XP and Windows Vista, VTCL gives the following errors on initialization of the first toplevel widget:
bad variable name "vTcl(w,opt,-background)": upvar won't create a scalar variable that looks like an array element
invalid command name ".vTcl.ae.sw.c.f2.f._Toplevel.t-background.f"
Along with these errors, the attributes for the toplevel widget do not appear in the attribute editor. Attempts to add additional widgets also result in errors and not editable attributes.
This error only applies to the Windows version.