Security Center service in SP2

I've installed SP2 on my two computers. I'm having
difficulties accessing my desktop PC from my laptop. I
suspect that the firewall of SP2 may be involved. However
I can't access the Windows Firewall Settings in the
Service Center. It pops up with an error message asking
if I want to start the service. If I click "Yes" an error
message pops up saying "Unable to start the service".
I've tried to start it manually using the Administrative
Tools, but then I get error message "1068: The dependency
service or group failed to start."

Any Ideas?

Thanks alot