I have spent the last twelve hours trying to work out what is going on with my Windows Form program. The program has been working successfully for over a year. Recently I decided to add an additional textbox which would contain a postal code accessed from a bank name file. This was a visual aid only and had no other function. I have various check boxes, which, in the past when clicked would highlight the accompanying textbox to show that it was selected, and then the program would perform one of a various number of tasks. All well and good. Now, however, after adding the informative textbox, when any one of the checkbox’s are clicked it goes back to the beginning of the program and wants to start reading the input file again. Please, don't state the obvious, I have checked all the checkbox’s and the corresponding events, they all look exactly as they should, nothing has changed. Has anyone come across a problem like this before, and if so what was the solution?