After Module updates got "Warning: require_once() "
It would be interesting to see if your problems could be related to the "memory limit", which might not be high enough (anymore), especially because of the "... have also added Workbench Media module ...".

Assuming this is NOT a multi site, consider editing your /sites/default/settings.php, and change the line to set the memory limit. If it is a multi site, then edit the settings.php file related to the site where you are experiencing the problem.

That line in settings.php should look similar to this:

ini_set('memory_limit', '100M');


The '100M' in it might be some other number. Whatever the number is, try to increase it with like 50%, or maybe even double it to see what happens after you do so (of course do not forget to save the file after increasing that number).

Another possibility that you may want to verify, is to "perform a clear cache" (it doesn't hurt, and occasionally helps solving various issues).

Curious to hear if that helps somehow ...