MMC crashes on fresh installation of SBS2003 R2

I have just tried two times to install Windows SBS 2003 R2.
The installation was sucessfull, I patched it with SP and other updates for 
all products.

Both installations ended up with a setup where the MMC keeps crashing when 
using the Exchange and the ISA plug-ins.

I receive the following alert with 3 options, each time:
"MMC has detected an error in a snap-in. It is recommended that you shut 
down and restart MMC."
1. Report this error to Microsoft and shut down MMC
2. Continue running and ignore error with this snap-in for the rest of the 
session
3. Continue running and always ignore errors with this snap-in, regardles og 
user or session.

If I chose either the 2. or the 3. option, the MMC will crash-hang the next 
time the error occures , and I will have to kill the process.
After clicking ok, I received the error message: "Error: 0x800401ff" -

Object has been released"

There are no peticular events in the any of the Event logs.
The error always happens when I open a firewall policy in the ISA 2004 
snap-in and chose the tab "Protocol", and in various irregular
situations on 
other child forms of the ISA 2004 and Exchange 2003 snap-ins.

Any solutions?

Thanks in advance

EDB Steen