"Exception Occured" Message

A Userform I am building was working as expected till I added two spinner controls.
These are each linked to a TextBox on the form and to a cell on a worksheet using the initialise and the change procedures for the controls.
They work the first time the form is displayed but thereafter if they are clicked (or if any other control on the form is clicked), a window pops up with the message "An Exception Occurred".
There is no indication of where that exception is. The window is not the ordinary coding error window.
It will be a big job for me to disentangle the relevant bits of userform and code to forward to enable anybody to fully solve the problem so what I am hoping can happen first is that someone will be able to suggest what may be going wrong. I am at a loss because I have never seen that window before.
John

Thanks for your suggestion which I will follow.
I have disabled all the code connected with the spinners and the associated text boxes and still the message appears. I have removed the controls altogether and the message disappears.
I will now add each part back one at a time and use the stop command and see what I can find out.
John