NTFiles did the trick.  rundll32.exe was the culprit.  I stopped the 
process, installed the driver (the serial was now unused), and now the 
tablet works just fine.  I can even reboot the computer and when it 
comes back up the tablet still works.

Thanks everybody for your suggestions!  I knew this was the right place 
to ask.  Too bad I didn't think of it a month ago :(

John Pfaff wrote:
> I'm using the tablet on another PC, one that doesn't have this serial 
> port problem.
>
> Paul Hutchinson wrote:
>   
>> Before you spend too much time trying to get the serial port working, have a
>> look at the release notes for your particular Wacom tablets XP driver.
>>
>> A couple months ago I went through the hassle of getting a serial port
>> installed on a new PC for an old Wacom tablet. Then I discovered that my old
>> serial Wacom tablet is not supported under Win XP SP2, it was in the release
>> notes, that I hadn't read, doh. Had to swap it with the USB tablet on my
>> Win2K PC (the Win2K Wacom driver did work with my serial tablet).
>>
>> Paul  
>>
>>   
>>     
>>> -----Original Message-----
>>> From: piclist-bounces@mit.edu 
>>> [mailto:piclist-bounces@mit.edu] On Behalf Of John Pfaff
>>> Sent: Thursday, January 18, 2007 1:14 PM
>>> To: Microcontroller discussion list - Public.
>>> Subject: Re: [EE] PC Serial Port
>>>
>>> I haven't installed the Wacom driver (not for lack of trying), or 
>>> connected the tablet.  The setup program won't install the driver 
>>> because the serial port is in use.  My problem is determining 
>>> what has 
>>> the serial port locked up and freeing it.
>>>     
>>>       
>>   
>>     
>
>   

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