So, you have your BHO ready for debugging and it’s just don’t work as you wish in IE8.
This issue happens after MS introduced LCIE – (Loosely-Coupled Internet Explorer) in IE8.
More information about LCIE can be found @ www.microsoft.com/windows/internet-explorer/readiness/developers-existing.aspx#lcie
This following will guide you through the steps of overcoming the issue:
1. Run regedit
2. Browse to HKLM\SOFTWARE\Microsoft\Internet Explorer\Main
3. Add a new DWORD called TabProcGrowth
4. Set its value to 0