ActiveX control gets freezed

I have a couple of forms ( both are MDI child) which has a date control ( User built ActiveX control) on it. Following is the description of the problem :
I open the first form in the normal size and use the form ( like accepting input form user) then with the first form opened, I open another form and maximize the 2nd form. Soon after I close the 2nd form, my first form is also maximised, which is not a problem, but the ActiveX control in the first form is freezed, I mean the control just appears to be a white strip.

Why is this happening like this ?? Please reply asap if any one has idea about this....