Please can you name the adaptor in question, there have been several issues the main being Intel 3495abg mini card and this was all to do with software and drivers. It must be pointed out Vista controls the wireless adaptor and not the software that comes with them as in XP and this cannot be changed. the drivers for all wireless cards that are Vista able work well, and once the correct drivers are installed all should be OK. There are exceptions and in my case i had to change the wireless card to stop wireless drops, i also used Intel drivers and not the Dell drivers at the time.

like you when the wireless dropped all the network dropped however once i changed wireless card and drivers all was well then work at it and you shall be rewarded.