Can you further explain your setup? It really sounds like you have a broadcast storm going on but its impossible to determine without fully understanding your configuration. I've never heard of incompatible switches. Since they operate on the second layer of the OSI Model a vendor would really have to do some work to make them incompatible. Broken makes way more sense, except switches rarely break without physical negligence.
Connecting switches to each other usually requires a bit of configuration, I couldn't find the 109 on the Netgear website so I'm assuming its an older model, and probably needs some basic features turned on, like spanning tree.
Have you gone into the configuration interface for the Netgear router? If you go to the Netgear website you can download an app that brings up an easy to use interface for the router. I have a Netgear switch and the Smartwizard finds it in a snap and lets me configure the switch in IE like a router.
Hope that helps,
-Rick
