Experimenting shows the default 10 is too small to handle all the logs spilled
at system statup and unix-stream("/dev/log"); needs to be changed in 
unix-stream("/dev/log" max-connections(48)); (32 is too small, I blame 48 on ATM)

The new max-connections enforcement introduced in syslog-ng 2.0.4 is 
quite "nasty" (the 10 connections default is in fact too low).

With the default configuration I didn't detect any warning but as soon I
started using yum to update/install packages I started seeing the
"Number of allowed concurrent connections exceeded" message.

Bumping the max-connections to 20 solved the problem (with the default
configuration).

     source s_sys {
         file ("/proc/kmsg" log_prefix("kernel: "));
    -    unix-stream ("/dev/log");
    +    unix-stream ("/dev/log" max-connections(20));
         internal();

I will try to update syslog-ng in my main log server to version 2.0.4
and see the result.


From the syslog-ng-2.0.4 NEWS file
----------------------------------
2.0.4
        Mon, 14 May 2007 11:47:48 +0200

        IMPORTANT NOTES:
        * This version of syslog-ng fixes a bug in enforcing the
          max-connections() limit for various stream-like sources
          (unix-stream and tcp). Previously this limit was not enforced,
          thus production environments may use an inadequate value.
          Validate your max-connection() settings before upgrading
          and check your logs for rejected connections.

...

IMHO for the default local system source it's better to be too big than too
small, and 32 was still too small on my system (without too many log-spilling
daemons installed)

syslog-ng 2.04 is now available in F-7 updates-testing.

Changelog:
The default configuration file now defines the number of max-connections for
unix-streams as 32.

   ...
   unix-stream ("/dev/log" max-connections(32));
   ...