When adding an overlay to a Google Maps implementation, be sure to read the documentation thoroughly, which I of course didn’t resulting in the fact that I missed the important part about XHTML and VML which on its turn resulted in the fact that it wouldn’t work in IE.
Quoting the solution here will hopefully help out others who don’t feel like rtfm’ing the Google Maps API Documentation:
“If you want to show polylines on your map (like the lines used by Google Maps to show driving directions), you need to include the VML namespace and some CSS code in your XHTML document to make everything work properly in IE“. The API is referring to this piece of code.
Now remember that y’all!