This site has been up for a long time, but now we are having issues with admin not loading magento.css. It's also causing issues with the frontend with forms when someone is submitting.
The error message in console is 404 failed to load skin/adminhtml/base/default/prototype/windows/themes/magento.css
while on server level it is set to /skin/adminhtml/default/default/lib/prototype/windows/themes/magento.css
I've included a screenshot. Has anyone had this issue before? It prevents me from removing images, uploading attachments and so forth.