OK, here's what I was able to dig up so far.

I commented out the RewriteRule for user.php and put in a different one:

Code:
#RewriteRule ^([^/\.]+)?/?$ user.php?username=$1 [L,QSA]
RewriteRule ^([^/\.]+)?/?$ invite_friends.php?welcome=$1 [L,QSA]
This works for when a person logs in, they go to the invite_friends welcome page, only problem is now they can not access their profile or anyone else's at all. The only way they can access their own profile is if they access the URL /my_profile.php . I think it has to do with conditions, but I don't know how to do it...yet.

During my search, I found a very cool page that generates .htaccess for you which I think is the neatest thing since sliced bread:

http://www.southeasttelephone.com/tools ... cessor.php

So, it's back to more digging unless there's an .htaccess guru out there who can help with this, I'd be ever so grateful (and I'm sure so would the rest of the vShare community).