Can adding a hub to the WAN side of my router cause network problems?

Answer 1

Try Adding a Switch insted but adding a hub must not cause any problem unless you have a good device

suggested device

3com
Dlink
smc

Answer 2

Do you mean you got from MODEM > HUB > to WAN port on the router? why would you do that. I'm not sure if it would cause problems, but I suspect it would.

One of the reasons for putting in a router is security. Having a router between the internet and your computer protects your computer. Putting a hub to split the signal before it gets to the WAN port of the router puts the non routed computers at greater risk.