Vista - Plug-in causes hang on program exit...

I have a relatively complex problem which nobody has been able to solve so far - so I will post it here in the hopes that someone can help me continue with my investigation.

3 computers - two desktops, one laptop, all running vista x64 (two ultimates, one enterprise on one of the desktops).

I have a principal (3D modeling) program I use, and it has various optional plug-ins. One third party plug-in is used for machining parts, and has a hardware key (dongle). It is installed on all 3, I plug the key in wherever I'm working. Function-wise everything is fine. (all this stuff is x86, no native 64 bit yet)

Now for the problem... On one computer (the laptop), if my machining plug-in is loaded, when I close the principal program, the window disappears, but if I go into Task Manager, I see it is still there. That is to say, it doesn't manage to exit correctly. I have to kill it manually. If I don't, every time I open a new instance, it stays stuck in there, at one point before I discovered what was going on, I had 6 or 7... which ran up the memory use, and that's how I found the problem.

If I unload the machining plug-in, the problem goes away.

On the other two computers (desktops) no such problem exists. The program exits normally, plug-in loaded or not.

So, there is obviously a conflict somewhere on the laptop that is preventing the program for exiting properly. I assume this could be any one of a number of things - drivers, other software installed, ??? All three computers have pretty much the same software loaded. One difference is that the laptop is an HP unit, with all the junk they put in there, the others are custom built units with installs from a retail OEM disc and no "bloatware".

How can I proceed? Is there a way to see what's hanging up when the program refuses to exit? Event viewer? Dependency walker? I'm a reasonably experienced user, but not a systems expert.

Needless to say the manufacturer of the plug-in says they "cannot reproduce the problem" and the manufacturer of the principal program says that if the program runs fine without the plug-in, then the problem is caused by the plug-in...

TIA, --ch

have you done a comparison of what services are running?
something to do with power management on a mobile system, maybe?

Well, there's like 80 processes running on one and more than 90 on the other... Gonna take some time to figure out what different from one to the other, but I suspect it is mostly the HP stuff, media center, etc...

--ch