Right - it wasn't that Endpoint Security was heavy on resources, it was the firewall feature caused problems on some of our machines (esp. those using a shared version of Quickbooks).
I will double check w our vendor as to the license username and password, but, originally we were able to install Endpoint Antivirus using the username/password provided by our vendor, so I'm not sure it's an issue w/ the license.
Our suspicions point to an ESET update - we installed the software late Dec./ early Jan. on several machines, there was an ESET update I think around Jan. 11 and I think something in the update has affected how ESET is working on several of our machines. We have had to uninstall the software, and reinstall it using the username / password provided to us by our vendor (which worked). We are trying to avoid having to uninstall and reinstall the software on all of our machines. We did not push the install out through our servers.
Thanks in advance for any additional insights.