I use the free Comodo Firewall by itself, version 3.0.25.378
This is setup on 2 systems (at home) where I am testing Windows 7 beta RC build 7100.
When attempting to update Comodo firewall, or it attempts to update itself, I get the error “One of passed string parameters is empty!”.
I used the same version of the Firewall with the Windows 7 beta (previous build, 7000 or so, I forget exactly) and the firewall updater worked properly.
The Comodo Updater is the only portion that is not working properly, the rest of the program is. I do know of course that this is why there are beta and Release Candidates of software and operating systems. I just figured I would pass this along to you to have the programmers look into it, to have a program working well when Windows 7 ships (Oct 2009 is last date I heard semi-officially).
I do not have any problems with any other OS I currently use the firewall on at my house (Vista x64 or XP). Please let me know if there is additional information needed.