I have exactly the same problem now!!
I'm moving from 5200-01 to 5200-07 ...
upon reboot, the system hangs with 0517 mount /usr...
I can't get into my AIX anymore...
I was even trying to do a preservation reinstall... but that won't work...
Right now I'm thinking to reinstall the entire system...
I don't know what happened with the update to 07, but it ain't good...
If anyone has any suggestions on this, i appreciate hearing them...
greetz