Usercontrol terminating before it should

I don't know why, and I cannot reproduce this in VB.

I have this UC, which is called from another UC running through Internet Explorer. Just after the Initialize event, it runs the Terminate event!!! Obviously, when the OCX tries to keep working with it, it hangs, and you have to kill Internet Explorer. I could not reproduce this situation when debugging it through VB. Not even when running in a common EXE. I also created a litte OCX (which is running in IE) and call the problematic UC from this OCX... AND IT WORKS!! Why the usercontrol terminates itself when I run it from the "real" OCX through IE. TIA.