It seems that you have an integration issue or a wifi adapter that is not working properly in a hardware level, the recommendation is to install the latest driver from the manufacturer's website or you can try the latest generic version at the following link:
If the issue persists please contact the system manufacturer for further assistance.
I have Dell Vostro 131 with N1030.
I loose connection in N mode only (like you, randomly). B/G works OK.
Also I always loose connection when another wi-fi computer enters to network.
In this case I loose connection forever. Unitl to disconnect--connect by hand.
I changed drivers, notebook location (relative router), played shaman, budda, christian music.
I guess Intel must increase programmer's salary.
I have the same problem in my Dell XPS l502x. I don´t know why but when the wireless is connected after a while (it could be minutes or hours) the card is disconnected. When i go to the device manager there is no Intel Centrino Wireless-N 1030 appears, but when i restart the laptopt it appears. I tried to update the drivers but it still persist. Also tried the MBV2000@intel.com solution but doesn´t work.