routers vs switches

Hi there!
I have a small network of 6 computers (all on a mixture of Windows OS) these are on an ethernet, and access the web through a LAN.
Our ADSL router is playing up, and I need to purchase a new one. However, I am wondering if the problem might also lie in the Switch? The connection to the internet goes down and the router freezes usually when our internet traffic is high. If I try to transfer a large file over the internet the router will almost predictably freeze.
I currently have ann MRI 8port 10/100 MBps Switch, and a DLink ADSL Router.
How can I tell if the Switch is doing it’s job properly?
If anyone can help me in this area, I will be really greatful.
Thanks.
-Angel-