nsswitch.conf meaningless?

Hello,

some days ago I noticed that nss_ldap stoped working.
Now I recompiled it with debugging enabled but it seems that it's never 
called.
No matter what I put into nsswitch.conf, I don't get any error.
What's the way to find out what's going wrong?
Shouldn't a entry like
group: dap files
in nsswitch.conf lead to an error message?

Thanks,

-Harry