Has anyone ever experienced wierd problems/errors with apps running on Toshiba, or any other kind, notebooks that were not recreatable on other machines?

One of my beta users for an app I wrote is having some wierd problems and is running the app on a Toshiba notebook. A couple of examples are:

1. He'll be doing data entry and click into a grid then all keyboard navigation in the grid won't respond. Click out of the grid and tabbing through controls works fine. This is intermittent as most times he can click into the grid and tab and arrow around hust fine.

2. He'll enter a form based on a parameratized view and nothing shows up even though data was entered in the past. Exit the form and reenter and the data is there. This is intermittent as well because lots of times he'll enter the form for the first time and the data shows.

I haven't been able to recreate any of these ever on my desktop development machine and I even tried doing data entry like he would with live data for an hour with no problems.

Any info or past experience with anything like this would be greatly appreciated before I pull out all my hair. TIA