Activation Query with USB devices

I have Vista Enterprise x64 installed and have been running both VMWare 6.0
Beta workstation and MS Virtual PC 2007 as I needed access to 32-bit OS's as
well as 32-bit with USB 2.0 support for compatibility issues. Probably about
6 times I added and removed my USB 2.0 device in VMWare, which was detected
to be add/removed in both the guest and host OS.

When looking through Eventviewer, I noticed that the following logs are
being added:

Source: Security-Licensing-SLC
Logged: 30/03/2007 04:43:56
Event ID: 1025

Grace period has been started. Grace days=30 Grace type=4.

Whilst my MAK Enterprise key has 15 activations, 12 of which remaining, it
is worrying me that using a virtual OS is flagging possible activation errors.

I say errors because my install is still activated, and running slmgr -dlv
from the command prompt shows my install to still be fully licensed.

Can someone shed any light as to why the above log is appearing? Thanks.

Surely there is someone who can shed some light on this?