I was unable to fix either the blank page or admin access problem. I eventually did a fresh install of XOOPS 2.0.18.1, installed all of the modules and manually copied the tables into the new database.
One thing I did notice... it's not advisable to copy anything but the module-specific tables because I got errors most times when I tried to copy a XOOPS core table (ie: comments, templates, etc) and had to revert to one of the incremental backups I was creating along the way.
Hope this helps someone.
On another note, I've just discovered that our new host is unable to accommodate us by creating a PHP.INI for virtual hosts. So NOW it looks like we're moving the bleeding site AGAIN. I'll create another thread in a more appropriate area asking for hosting advice.
Thanks to everyone for their help!