LG TinyMCE: Error 501 issue?

I’m migrating an EE installation from my localhost to a client’s web server and was trying to install LG TinyMCE. Everything looked OK but when I went to change the configuration setting telling it where to find TinyMCE I got the followinng server error message:

Error 501: The server cannot complete the request because it encounters an error Header values specify a configuration that is not implemented. ModSecurity, web application firewall, possible secure attack prevention.

I have a feeling that it’s due to the way the server is configured (it’s a small local hosting operation, I think) as I did similar migrations to Dreamhost and MediaTemple and they both worked a treat.

Is it them or is it me? When I start to delve into server issues, my eyes get all glassy and I enter a kind of fugue state, so anything you could do to point me in the right direction as to things I can check for would be great.

[Edited to add: When I say “everything looked OK”, I mean the install looked fine. The actual TinyMCE WYSIWYG functionality in fields that were set to it wasn’t actually working.]