Description of problem: The HP-UX accept() can give an EINVAL if a new connection arrives and is signalled to select() but is closed before accept() pops. The child process treats this as a fatal error condition, terminates, and is replaced as normal. A related fix to handle HP-UX accept() returning ENOBUFS was committed upstream a while back: Stronghold should handle both ENOBUFS and EINVAL returned by accept() as non-fatal error conditions on HP-UX.
Fixed in 4.0j, stronghold-apache-1.3.22-21.