What active checks? service? host?
what version are you running?
why are you posting the same problem in a nagios thread and in the icinga section?
Have you tried running the checks by hand?
In the other thread you say the checks return a NULL, so are they being run and return NULL or are they NOT running?
did you update something?
If you ask for help "ASAP", at the very least you should try giving some useful information...