We're using a Bell 2Wire Gateway modem/router as our only hub (with some switches attached).
Intermittently, but frequently when a large download is initiated, all computers on our LAN lose the ability to lookup websites (ie: DNS lookup fails). Pinging or accessing the IP address directly works as usual, but any name lookups fail. A reset to the modem usually fixes the problem. This happens daily at least once a day, though I haven't observed a pattern to when it occurs, other than large downloads often trigger it.
We are not running our own nameservers. Our ISP is Bell Sympatico in Canada, if that's of any help.
What could be the problem and what steps should I take to resolve it?