We've got moodle 1.8 installed and it's all been going great.  Now today I discover no one (not even admin) can open any files on any courses.  What I mean by this is that all looks well, you can go to courses, opens lessons and upload files etc. but if you try and open a resource that has been there for ages and working you get an error saying "Internet Explorer cannot display the webpage". 

Anyone got any thoughts?  Don't think we've changed anything!

Dave