Okay, I turned on the error logging:
for the user_registration page, I get
Fatal error: Call to undefined function virtual() in /hsphere/local/home/claypool1/test.realdesigngraphics.com/users_Registration.php on line 5
line five is
<?php virtual( "/Connections/ClientBase.php" ); ?>
for the user_login page and user_profile I get
No input file specified.
I don't have a clue what to look at to fix these ...