Angels have the Phone Box
Hi pitman44 and welcome to Tenforums.
I would say try a repair to Office - right-click Start>Control Panel>Programs and Features, wait for the installed programs list to populate, then highlight Office and select Repair from above the window. You should get two repair options, a local one, and an online one. The local one is quick, and may do nothing. The online one is almost like a complete new install and will require you to sign-in to reactivate.
You say you've got all add-ins disabled - that would have been my next guess. But the bandwidth issue is really odd/suspect. What happens with the bandwidth if you select "Work Offline"? I would run a Malwarebytes Antimalware Free (full) scan to see if anything comes up, just to be sure. I would also view the Reliability History (search in Cortana/search box), and see if any clues are found there.
That's about all I can think of ATM. Hope it helps.