I just had this problem with some teachers in our VLE, we are using 2.6 and Essential, to solve it I just restarted our web server. All works fine now.
In reply to Clive Gibson
Re: Moodle not enabling adding resource or editing existing
by Mike Clarke -
How do you restart the server? My site is hosted with a 3rd party hosting provider Pickaweb
I doubt this is anything to do with the server, its more likely to be the theme as it works in Afterburner. Are you using Internet Explorer 8 or 9 by any chance?
In reply to Mary Evans
Re: Moodle not enabling adding resource or editing existing
by Gareth J Barnard -
Whatever it is, its still a JavaScript issue as the '+' icons are not showing up. Ok, as Afterburner (I don't think) uses jQuery and Essential does (correctly) then please do as Richard suggests and press F12, reload the page and look at the 'Console' for errors and post them here. As the problem only happens in one module and not another it will be to do with what is 'special' about the icons.
In reply to Gareth J Barnard
Re: Moodle not enabling adding resource or editing existing
by Mary Evans -
Could this be a Course Format clash Gareth?
I'm looking at this now, and have JS disabled works OK with Collapsed Topics, as the Add resourses use select menus and they work fine, same with the 'more' arrows as these also appear along with all the editing icons rather than the Edit dropdown.
In reply to Mary Evans
Re: Moodle not enabling adding resource or editing existing
by Gareth J Barnard -
Maybe, maybe not. That is just speculation. With JS disabled, of course it will work! I repeat, the console will show up the errors and provide the evidence required.
P.S. Collapsed Topics uses a mixture of pure JS and YUI. So will not clash.
In reply to Gareth J Barnard
Re: Moodle not enabling adding resource or editing existing
by Mary Evans -
Well everything on this forum has to be speculation until someone finds out the cause of the problem, The fact it can be a dozen thing is frustrating, and is not made any easier when people go off and forget to say if the problem is fix because they forgot to do something.
I'm just thinking back a few years when a course format I downloaded and had a similar problem and you found out the cause of it. It wasn't one of your course formats it was one that added a forum that just allowed anyone to add a comment. But the code was bugged with the UTF8-BOM remember?
We, (you and me) spent ages tracking it down. Those days were exciting...now these bug hunting sessions where everyone is blaming Essential, is getting boring, as the more you make Essential so well built, which is fantastic, I am beginning to worry that you are unearthing more bugs. 
In reply to Mary Evans
Re: Moodle not enabling adding resource or editing existing
by Gareth J Barnard -
Hi Mary,
I do - the UTF8-BOM is horrible! It think one of my course formats did suffer from it once. I think the plugin DB has been updated for BOM detection.
The snag is, that the theme is the most visible candidate for errors when in fact its often buggy third party code. I'm not sure if Turnitin have yet to release a version where they use jQuery correctly and thus prevent clashes.
Sorry, I have no desire to put bugs into Essential for Sherlock Evans to solve ;)
Gareth
In reply to Gareth J Barnard
Re: Moodle not enabling adding resource or editing existing
by Mary Evans -
In reply to Gareth J Barnard
Re: Moodle not enabling adding resource or editing existing
by Richard Oelmann -
No they haven't Gareth (TII/jQuery) but so far I haven't had any problems with it and the (old) Essential my work theme is built on or the plugins we're using. At least none that are jQuery related.