These are symptoms of a fine locking problem, which usually means that the server is trying to use a synchronization file on an NFS filesystem.

Because of its parallel-operation model, the Apache Web server needs to provide some form of synchronization when accessing certain resources. One of these synchronization methods involves taking out locks on a file, which means that the filesystem whereon the lockfile resides must support locking. In many cases this means it can't be kept on an NFS-mounted filesystem.

To cause the Web server to work around the NFS locking limitations, include a line such as the following in your server configuration files:

LockFile /var/run/apache-lock

The directory should not be generally writable (e.g., don't use /var/tmp). See the LockFile documentation for more information.