WBR-5400 Level One Router problems

Hello.

I bought a WBR-5400 MIMO Level One Wireless Router. Connected it to the modem and my PC. Fired it up, and set it up with my connection details etc.
I use a L2TP connection with it, meaning its not a static IP connection, but a Dynamic.

The problem is, after being connected for a few minutes something happens to the connection, and from that point on i can only connect to serveral websites, and slowly if even possible, and only a few programs have a connection. For example, after those few minutes where everything is alright, Messenger can't connect anymore, and so can't other programs, but others, like Ventrilo for instance, or even my Spyware Doctor Update work online.

I thought maybe its the MTU settings that are incorrect, so i went into the /sysp.htm page (it's where you setup the MTU size for PPPoE and Static/Dynamic IP connections and 2 other things i dont know. (H232 Data Port and Ctrl Port).

I set the MTU's to 1490, and the H323 i kept at 0 (default i think), but still after a few minutes of a normal connection it goes wierd again.

When this occurs, this problem, the connection is still alive, i still see the connection timer running on the router web page, but its like disabled somehow, or crippled. I need to restart my computer and reboot the modem for it to go back normal again, but then it happens again after a few minutes, and you get the idea...

If anyone has an idea what's going on PLEASE help me, im getting desperate, and i need the router to work.