In Tridion 2011 SP1 I installed a GUI extension and fiddled around with the configuration and setup. The CME GUI does not load, and in the browser's console there is an error:
Value should be a function.
See screenshot attached. What could this error message mean?
In my case the error only occurs on IE9, not in Chrome. Clearing browser cache, restarting browser and IISreset did not resolve the problem.
If the configuration is correct and all the JavaScript files for the extension are deployed the issue is that something (browser or web server?) is aggressively caching stuff. I could resolve the issue by increasing the modification attribute in Tridion\web\WebUI\WebRoot\Configuration\System.config.
<server version="6.1.0.55920" modification="7">
The error could be reproduced afterwards by removing the code from one of the JavaScript files in the GUI extension and replace it with bogus text.
Normally the partially loaded GUI is caused by a bug in your javascript. When this happens in my own extensions it's 90% the missing of a ; at the end of a line.
I'd recommend re-checking your javascript and maybe add some console debugging to see how far the code is going.
Are you using jquery in the extension too? I had a similar problem and solved changing the version of jquery that I used and referenced in the extension config file. (changing 1.10 to jQuery JavaScript Library v1.4.2).
