SharePoint - distributed cache

A colleague found the other day that:

If distributed cache on dedicated servers is not working, with error is ERRCA0017,make sure app-pool account(s) are in WSS_ADMIN_WPG on the dedicated distributed cache servers.

Oh, and you really should be on CU 6 of App Fabric.

http://www.microsoft.com/en-us/download/details.aspx?id=46802