See if this works.
Correct your home page to the one you prefer, then immediately do the following:
Backup the registry and/or export the following keys:
go to Start>Run, type regedit. Navigate to:
HKEY_USERS\.DEFAULT\Software\Policies\Microsoft\Internet Explorer\
Right-click on the Internet Explorer key, choose new>Key, name it Control Panel.
Right-click on the Control Panel, chose new>DWORD value, name it Homepage. Right-click
on Homepage, choose modify and type in the number 1.
This should lock your home page, so no other web site can change it.
Then navigate here and verify the homepage is correct:
HKEY_CURRENT_USER\Software\Microsoft\Internet Explorer\Main
look for the Start Page entry.