It's been three or four weeks ago. Sorry it's taken me this long to respond. I've been busy with other things. I'll try to post the project when I get home. Basically, the app uses a combo box to allow a user to select a range of values. Works flawlessly on my machine, but on another person's computer it raises an exception that seems to be related to the combobox. I redid the project and used a textbox for user-input instead of the combobox and this took care of the problem. Still, I'd like to understand the exact nature of the problem, for my own edification. I may need to email the zipped project rather than posting it, because it was for a C# programming school assignment here on DC...