Also, that ticket seems to assume the reader knows what problem it's fixing. It's not entirely clear to me. Presumably a problem that I don't have or don't know I have.
Sounds like a configuration issue with your web server.
This sort of thing is often caused by (in the case of Apache, anyway) by over-zealous configuration of tools like mod-security. Anyway, check your web server logs to see if it logged *why* it blocked that script and go from there.
I would start by opening the Javascript console in your browser (F12 then select the 'Console' tab). Recreate the error(s) and check for any (red) error messages in the JS console.