Unable to Read USB port since upgrade to XP SP2

I have a program that uses a control called pcogarmin.ocx. This control communicates with a Garmin GPS unit through a USB port. It was working great until some of my users were upgraded to XP service pack 2. Since then, they are no longer able to see their GPS via their USB port. NOTE: These users do not have Admin rights to their computers. Those with Admin rights to their computers are able to use the USB ports with no problems. I have contacted the administrator of the PCOGarmin.ocx control who had this to say:

Its not related to PCOGarmin. I also use PCOGarmin im my GPS-Software TTQV. We have many thousends copies out. The problem are the security patches of XP-SP2.

You should grant full acces to this part of the registry in HKLM , where the software stores its data and also to the folder in c:\program files\ where your software is installed. My software TTQV does this during setup which has to be done as admin. Then a normal user can login and use TTQV and also PCOGarmin without admin rights.

I have done this but it still doesn't work for me and I haven't been able to get back in touch with the administrator.

Also, other programs connect up to the GPS via a USB port just fine.

I'm guessing it is a permissions issue somewhere in the registry. Anyone have any suggestions??

Thanks.

C