Parts of the admin area don't work correctly anymore

[ESV]

Hello,

 

Since a few days we've begun experiencing constant problems with our admin area. Some of the problems that we've encountered:

 

• The menus don't expand anymore. To see the submenus of a menu you need to click on it.
• Some (sub)menus won't even open at all at times. Advanced Parameters for example often won't open up. When it does submenus like Performance won't open
• We can't open up the localisation files at all. It refuses to let us select a Language.
• The WYISWYG editor for the CMS/product/category pages doesn't work anymore. It just defaults to a pretty much unusable, two-line high HTML depiction of the content.

 

Our third-party tech support can't seem to pinpoint the problem, so I was wondering if the community itself had some experience with this problem.

 

Thanks in advance,

Stefan