WinForms problem with mshtml and ie9

IE9 appears to have broken my mshtml com based WebBrower html editor in my 32-bit winforms .net 3.5 application. (It has to be set to开发者_如何学JAVA 32-bit due to an activex USB device controller I have to use.)

The bug is erratic - it doesn't happen on my system. If my customer runs IE9, and then my 32-bit application with the WebBrowser based html editor, my app hangs, no response. This did not happen with IE8.

This is so screwed up I don't even know how to formulate the question.