AH! TJKeeran, for the win!
See, Paradiizee was helping me with my site, but hes been gone for about 1.5 weeks now (school called!) And I'm betting he created the constants.php file that is in the link TJK mentioned.
I renamed it.. changed my default app back ( define( 'IPS_DEFAULT_PUBLIC_APP', 'forums' ) and voila! We are all fixed up!
Thanks to all that offered help, and a special thanks, TJ, for the winner.
ps.. there is not 1 single 'socialengineforum mods' on my site. I copied their front page layout, but everything aside from the html and absolute essential .css for that html is ripped out.
Everything else is furnished from here, butchered by me, or bought.
TJKeeran? This issue is resolved and can be closed. Thanks again!