>>Is form becoming irresponsive when you start it, or after some user interactions later?
>
>I invoke this form several times, it operates just fine, but then it stops. Using Exit button makes it responsive again, then it works for some time, then again after I invoke it it doesn't react and produces a sound of non-reaction when I try to do anything with it.

Most likely, you should activate timer in Form.Activate event and not before it.