I'm not sure if Plesk upgrade to 10.3.1 is responsible for this issue, but it started occurring after a server was upgraded to Plesk 10.3.1.
Product: Parallels Plesk Panel Linux 10.3.1, version: psa v10.3.1_build1013110726.09 os_CentOS 5
Operating System: CentOS 5 i386. Kernel...