Charter Spectrum conversion has introduced common computer lockups

My client has 3 physical locations, all just switched over to Charter Spectrum Business running on an Engenius ESR600 wireless router.  2 locations have no problems ever.  The third location has 6 computers, of which 5 will lockup using the AMS360 website.  The computers have never frozen except during AMS360.  The computers never once froze before switching to Charter Spectrum.  The 6th computer is the only laptop in the office and doesn't use AMS360 much if ever.  So I began testing power to computer stations, but no power issues could be found at the two highest occurrence PCs.  To make things worse, the problem never effects two computers at the same time.  The software can run in IE or Chrome, and the problem are the same on both browsers.  Most of the time, the browser is not responding and never recovers, but you can open another instance of the browser and work just fine.  On a slightly more rare occasion, the user will report one of the AMS360 tabs will go gray (Not responding), and when the go to another tab and work there for a short time it may lock up (No mouse, keyboard or any input).  They have waited an hour to see if anything will change, which it doesn't.  I don't really know the actual frozen vs not responding broswer %.  I have seen first hand an unresponsive PC at this client and the browser not responding.  All computers are Windows 7 SP1 64-bit.  They are a mix of Lenovo ThinkCentre and Dell Optiplex computers.  I have installed all updates and drivers to the worst case computers.  On the AMS360 site, a user may have several or more tabs open.  Typically they don't have any other sites open.  Norton Security is the antivirus installed on all computers.  The network switch is the same as before.  The network switch and router are connected to a UPS.