com port 1 fail, no standby

This has happened to me twice now on my new HP a340n
desktop. When I hit the standby key, I get the following
message:

The device driver for the "Communications Port (Com 1)"
device is preventing the machine from entering standby.
Please close all applications and try again. If the
problem persists, you may need to update this driver.

and the PC won't sleep. It continues to apparently work
fine.

The first time it happened, I backed up thru 3 restore
points and it finally worked. I was loading software
applications and figured somewhere along the line one of
them hosed up the PC.

I carefully reinsatlled my software, and set a restore
point each time I succesfully installed an applciation.

Today, I've been using my PC, not installing anything and
it's been fine and standby has been fine too. Then HP
blasted onto my screen and did an "HP instant support
auto update", downloaded 3MB files and installed them.
There was no query "do I want them". It took the PC
several minutes to do the mandatory restart. I ended up
with a blank blue screen for a couple of minutes and then
my icons appeared. I immediately did a restore to
yesterday when all was well, and it boots up fine but now
my standby/COM 1 fail problem is back.

Any ideas?? Thanks