Internet connection works for only a short time after startup

[yoshibear1009]

Hello, I've just installed Ubuntu a few days back for the first time, and all of a sudden yesterday, my network connection began to have problems. It works perfectly directly after restard, but only for 0~30 minutes. No amount of waiting corrects the problem, do its clearly not a connection/ISP issue. Other computers in the household connect as well, as long as mobile divices.
When I ping google/yahoo/anywhere when the Internet is down, it returns with

ping: unknown host yahoo.com

On a side note, another issue I've been having is that during boot, the screen goes black with a box stating 'Input not supported', and I was wondering if there was a way to fix that.

EDIT: I'm using a wireless connection, by the way.

Thank you for reading through my post
~Yoshi

[Aaron Christianson]

It sounds like some kind of hardware failure, like maybe the wireless card overheating or something.

Does your computer get very hot when running Ubuntu? There are things like laptop-mode-tools and the jupiter applet that you could use to throttle performance and control the temperature to some extent, if that turns out to be the problem.

I can't think of anything besides hardware, but maybe somebody else can chime in.

[yoshibear1009]

Checking over my computer and the innards, it seems to be much cooler than when I was running XP whilst idling: the fan is running quietly as well. There's next to no lag whilst performing generic tasks.
When my internet's functional, I get a ping result from the sites; rather high result, though, but that's just a result of season/time.