Strange taskbar behaviour (notification area)

Ei system 4415 Laptop, Celeron 2.4 GHz. 248 MB of RAM, Windows XP Home
Edition SP1.

I'm running Trend Micro Internet Security and connection to my home network
is via a MA111 Netgear USB adaptor. The notification area fails (no icons
except MSN messenger icon) if I boot up with antivirus & firewall software
running *and* the MA111 USB adaptor plugged in. The notification area works
normally if either one is missing. I have the same problem if I run McAfee
Security Centre (AV and firewall). If I boot up the laptop first with any AV
running, (Trend or McAfee) then plug in the adaptor, everything works fine.
The notification area fails (no icons except MSN messenger icon) if I boot
up with antivirus software running *and* the MA111 USB adaptor plugged in.

The "hide inactive icons" box is unchecked, and there doesn't seem to be any
reference to the problem on the Microsoft website, or in the Help and
Support section. Un-checking and rechecking boxes such as the "show icon in
notification area when connected" in network connections has no effect; the
icons simply refuse to appear.

I have tried AdAware and virus scans in safe mode, and the laptop appears to
be parasite free - and whether the notification area works or not, I connect
to the network with no problem.

Any ideas?

TIA.

--
Falcon:
fide, sed cui vide. (L)