It seems that the iii and most unbelievable choice is the really one.
Is there any non-standard services running at startup?
Did you try to grep your old configurations? I mean grep your old IP in the /etc to see if any redhat tool is also storing this data for a possible recovering after reboot or something like.
If your computer replaces your old configuration, it must be somewhere, don´t you agree?
If you try to change your configurations using RH tools, the reboot problem does not happen, right?
I don´t like the customized tools bond to Linux distros, and that made me to avoid RH. The kind of trouble you have is not rare, as the companies feel ease to do non-standard things in the system.
The best you do is to tame your distro. As the time passes, you learn to live with its oddities.
By now. Make this try. Search the whole root if needed.