Hello,
on a CentOS 6 amd64 setup (latest free LSWS version) I'm receiving a 503 for each PHP request and the following entries are in stderr:
2012-08-21 20:02:14.216 [STDERR] libgcc_s.so.1 must be installed for pthread_cancel to work
Of course I then checked for libgcc, but it's installed...