Any other reason VBA/macros aren't working?

Hello,
We are a company that has a CorelDraw plug-in that is an installation, then it comes up when one of our CDR artwork files is opened. We have updated the code for CorelDraw X4 users and have many customers who use it with no problems. There is one customer who is using a full version of CorelDraw X4, on XP and is having issues bringing up our corel (Macros/visual basic) plug-in. He spoke with Corel and they did find some issue with other software on his computer, conflicting with the Macros in CorelDraw, but that was fixed. We have double-checked everything relating to our software and have tried things like lowering the CorelDraw security settings and turning off Norton. The only way we can get our plug-in to come up is if the image is open in CorelDraw and then we go to the "run" feature on the Windows Start Menu and type in our code to pull up the plug-in. We haven't had any luck to get it to come up automatically. Anything else we can try to help him out? Any help would be appreciated.
Thanks,
James