When you uncheck the Compress WebResource.axd link, you are not disabling WebResource ... you just are disabling the compression of the WebResource.axd file. The compression is purely an optimization so a smaller script is sent to the browser (all
the white space is stripped out). But the amount of performance you gain with this is negligible at best. You won't even be able to measure the difference in performance it's so miniscule.
When you had the Compress WebResource.axd option checked, there was a problem on the server and BE was not able to download WebResource.axd and serve it to the browser. Because of this, the browser was not receiving the normal WebResource.axd script
contents. The Contact page makes use of some of the WebResource.axd functions .... but because the script was not loading on the browser, these functions could not be called.
Now that you've unchecked Compress WebResource.axd, the browser is able to load the script contents from WebResource.axd where the required functions exist for the Contact page to function properly.
So, nothing to worry about. You're in much better shape now.