Do you have any cordless phones or bases nearby, especially on a line between your notebook and your router? Cordless phones work in a similar frequency range and can cause interference.
Another potential source of problems could be if there is any large power cable running between you and the router, like for a water heater or a range. A heavy current in a big wire generates a substantial local field and if its right on bee-line between you and the router, it could interupt service.
Lastly, check into your local power supply, there can sometimes be significant variations in power that while not enough to turn off the lights or reset your clocks, could blitz your connection.
Try keeping a log of these interruptions and see if there is a pattern. If there is a pattern, try moving when you next expect a disruption and see if that helps. Wouldn't hurt to try that anytime and see if it makes any difference.
What type of connection do you have, dial up, cable, DSL? What is the physical relationship between your notebook and your router.