Problem
F-Secure for Microsoft Exchange (FSMSE) continuously causes crashes to INETINFO.EXE causing it to "terminate in an unusual way".  This is version 6.40+

Removing FSMSE and rebooting causes these errors to go away.  Reinstalling, even with latest hotfixes, et al. cause this cryptic message on the console.

Event log complains that various Exchange related services failed to stop in a timely manner - POP3, IMAP, HTTP, and IIS worker processes complain that they "failed to terminate" properly.  OWA, and POP3 access appears fine - but system is constantly recycling threads.

Faulting application w3wp.exe, version 6.0.3790.1830, faulting module davex.dll, version 6.5.7233.28, fault address 0x00078f33.

Event log mentions a DCOM "{9DA0E0EA-86CE-11D1-8699-00C04FB98036}" failing "local activation" under the SYSTEM account.

Solution

Ensure Windows 2003 SP1 or later is installed; Exchange 2003 SP2 is installed.  Disable DEP except for critical system services as troubleshooting.  If problem persists...  Grant the DCOM permissions for local launch and activation:
Find this DCOM in Component Services (Administrative Tools).  Should be under Computers, My Computer, DCOM Config, at the bottom.  Right click on the {9DA0E0EA-86CE-11D1-8699-00C04FB98036} node, properties.  Check the security tab; add SYSTEM and grant local launch, and local activation permissions.  This is related to the EXCHANGEIS store service.
Re-enable DEP and do further testing.