My modem keep failing in to give me packets(i think thats what is happening), or the router?

This is the problem:
At random times i disconect at everything im doing in the internet, any applications like msn, online gaming, webpages wont open, etc, except for the icon that sais Wireless Network Connection it stays like if my connection was fine :x

I think is my modem because when it happens, because when it happens my when i try to open a webpage its send me to a webpage of SpeedTouch(ss below), in that webpage i can see the brand of the modem: SpeedTouch, and it tells me to click on the link register a different user, or something like that. When i click it ask me for the Username/PW, i forgot them so i dont bother to fill it.

My router is a WRT54G v8.00.0
My modem is a speedtouch 536

This is what happen when it starts, also in online games everything freeze at this point, and msn will stop working(like i sent msg to peoples and thet dont recieve and viceversa:
ImageShack - Hosting :: image01mszi8.jpg

Then a couple seconds after that, if i try loading any webpage it wont open, but will show some webpage of my modem(the one mentioned before). Whenever that webpage show it means its fixed(everything get fixed i mean):
ImageShack - Hosting :: image02mshl7.jpg

I have mixed feelings about those particular routers... I have seen some good comments... but many more complaints.
I don't use wireless personally-- but in forum posts that particular model comes up a lot.

Have you tried resetting it (unplug the power lead, let rest 2 full minutes) replug ?
Checked all the security settings ? (in the router)
upgraded the firmware

Tried everything except for upgrading the firmware.

You have a Firewall in your router ?
Or a software firewall ?
How do you logon to your router?
hopefully you are not using the default settings as this is very unsafe.

Ok, i have new stuff to say.
I have no firewall or such.
I have 1 modem and 1 router, the router connected to the modem, from the router there are 3 cables ethernets that go to 3 different PC, and other 2 PC(1 of them laptop, and the other one my desktop) have wireless.
My Desktop(wireless) have the problem.
My settings at the router are all default, except for that it have a password and a static IP.

I suggest you check with your ISP

Most DSL modems have a "built-in hardware firewall" some are better than others-- but they're all SOMETHING.... and they need to be configured BY YOU-- so nobody can get into your PC.

Security experts agree that an unprotected Windows PC on the web will be infected within 12 minutes.
This is a proven theory-- in test after test.
I run a good hardware firewall AND a software firewall for extra measure.
To go online unprotected is not only risky to you... but to everyone you know.
many viruses are setup to access your "address book" on your PC...
and E-mail itself to all of your friends (without your knowkledge)
which ususally does not make you too popular-- even though you did not know about it.