It's happened a few times, I'm not sure how to diagnose/debug, so any advise would be appreciated.

Symptons:

• sometimes the router will randomly disconnect; the connection icon on my desktop (wired to the router) gets that yellow "!" symbol that tells me my connection just went down. At this point I'm unable to ping the router.
• afterwards I try to reset the router by removing then reconnecting the power jack on the router side (this is the fastest way as I can't reset the power strip it's connected to without rebooting my desktop. the router has a reset thingy, but it's one of those things where i have to find a pin to stick into the hole, and when I get disconnected I usually need to get reconnected immediately so I just pull and put back the power jack), but even after that the connection has the same state.
• after the router reboots, if I try to connect to it using a wifi device like my ipad, the ipad prompts me for the wifi password even though it had already "remembered" all the settings for this router forever
• after i finally decide to reboot the power strip, and my desktop and the router boot up again, the connection returns to its normal state somewhat and i'm able to connect to it as normal using the desktop and wifi devices.

What do I need to check the next time this happens so I can figure out the problem? Is it possibly because we've been using the power jack on the router as an easier way to reboot it? Should I be shopping around for a new router?

If it helps, the router is a DLink DIR-300