Noticed this error yesterday with one of the resources. He was trying to add an administrative task to his timesheet and he was getting the following error.

I did try to replicate this on a different machine, but the feature was working OK on other machines. Also, checked few basic things like permissions etc., and everything seemed ok. So, I had the resource who had an issue retry this after sometime, and the issue went away. So at this time I am inclined to think that this is a network glitch. Will update if I figure out anything else.