Does "loadable object" refer to anything other than Tk/canvas.pm?
Yes - in this case it's referring to "auto/Tk/Canvas/Canvas.xs.dll" (or perhaps "auto/Tk/Canvas/Canvas.dll") - and that file needs to be in one of the @INC directories.
You'd expect it to be in "C:/Strawberry/perl/site/lib", but it could also be in one of the other @INC directories.
The first thing to do is to try reinstalling the Tk::Canvas module.
If that is done, then things should start working again.