Pb with custom control at design time

[Frédéric Mayot]

Hi,

I have a simple custom control in a web control library. The control only
inherits from a validation summary. (No code, just a class which inherits
from a .net webcontrol !)
Now I use my custom control in a page : OK.
Second step, I create a user control (ascx) which includes my custom control
: OK
Third step, I use my user control in a page : problem !! At design time, the
custom control says "There was an error rendering the control. Specified
method is not supported". At runtime, it's OK.

What is the problem ???

Thanks,

Fred