I have run into problems where an IP address that's NOT actually allocated on any interface is listed in plesk, but from the sounds of it some other issue is affecting you.
Please can you be more specific? When you have to say "have to go in and repair" what do you actually mean? Into Plesk?
If that's the case then it is possible that the network interfaces are not coming up before Plesk starts (try delaying the plesk startup). Or into the data centre because the network interface isn't running? If that's the case then there may be something totally non-plesk going on on the network side. Plesk 10 (11 is different) should not touch ifcfg files at boot and normally doesn't do anything network related (though there are exceptions).
Or something else again?
Is there nothing to see in dmesg or boot.log or /var/log/messages relating to network/ethernet on reboot that might help you pinpoint the issue?