I guess you can log in with ssh and check if the filesystem is read only?

The web interface loads fine? Not sure what you mean by no changes to cgminer can be made, is there an error when saving settings?

Have a look under Status -> Cgiminer configuration.

What does the field "API Allow(Default: W:127.0.0.1)" say? Does it actually have W:127.0.0.1 as settings? Without it the web interface can't read the cgminer logs