Strange, first time I see this error, after a quick search about ERR_CONTENT_DECODING_FAILED I found this:
It happens when your HTTP request's headers claim that the content is gzip encoded, but it isn't. Turn off gzip encoding setting or make sure the content is in fact encoded.
So normally FileUltimate gzip encodes its resources like CSS and JS files and caches them in a temporary folder. Do you see any related errors in Windows Event Viewer? Maybe for some strange reason (IIS configuration?) it fails to gzip the files on your server. Also please specify the FileUltimate version you are using. Let me know.