PowerPoint activeX control displays BIG RED X

Question

I have made a user control using c#.net and made the control as COM interop along with COM visible true. It built & registered  by "regasm" successfully. My control is visible in power point 2010 under "More Controls" option and can able to add it in slide. The problem is after embedding the control in slide (in design time) a red color "X" sign display inside the control instead of the actual visual appearance of user control. but when i start slide show, the User Control display its own interface (GUI) and when i stop slide show again the interface disappear & display red "X" sign.  How do i correct this problem??

Office Version: Office 2010

Program:PowerPoint

Operating System:Windows XP

Visual Studio : 2008

Working Framework : 3.5

Using Language : C#