It’s probably the same root cause so I suspect fixing one will fix all, but just in case I’ll mention that clicking edit on any item sets also throws an application error. Item search gives an application error, but player search is working fine.
I dare say that issue (and the same happening when you use the item search function) is not connected to cookies at all since I'm getting those errors in a sandbox environment as well.
It's probably something that has to be solved server-side not on our end.
You may notice some hiccups in the site over the next couple of weeks, as we are making some (hopefully) under the covers changes to how the site works.