I have a comcast cable modem with a wireless router to use my laptop.  The laptop sees the wireless router, and sometimes connects to the cable modem.  After some short time, however, I lose the wireless connection briefly (even if I am next to the router) and then it is restored.  However, I cannot restore the connection to the modem and the internet without rebooting my laptop.  I have replaced the modem, wirelss router, and tried this with other laptops of different manufacture, all have the same problem, so it is not a local hardware problem.  All my cordless phones are 900 MHz and I cannot think of any other source of interference.  I have no problem with my desktop machines hardwired to the router.    The comcast folks came out and checked the signal strength, and they said it is good.  What now?