Network init locks up hard drive

My wireless connection takes an unusually long time to initialise, during
which other applications appear unable to read from the hard drive. The drive
isn't grinding most of the time, but any program launches in progress will
freeze up until the moment the networking tray icon starts responding (before
the load is complete clicking the icon does nothing at first but later brings
up a correctly-sized, but empty, info box), at which point everything returns
to normal. This happens on each boot.

I've tweaked my services before now, but even booting normally through
MSCONFIG doesn't help. My hardware is Intel Wireless 3945ABG.