If your goal was to communicate with the parent while the second dialog is displayed, you shouldn't be doing this by invoking a modal dialog.

This is probably what's happening in the program (or something similar):

The problem is that for a modal dialog, it's parent's message queue is halted until the dialog is disposed of. You have a timer set, but the main dialog's message queue becomes blocked and can't process the timer messages when the secondary modal dialog is displayed. This probably screws up the messaging, and you get all sorts of problems.

Modal dialogs were meant to process independent of the parent, since the parent can't do anything (even get its own messages) until the dialog is closed. This is enforced in a modal dialog since modal dialogs have their own private message queues that are run instead of the parent's message queue.

You should either stop the timer before invoking the dialog, or use modeless dialog boxes, or possibly integrate the controls from the "set" dialog into the main dialog.

Regards,

Paul McKenzie