Try reuploading them. Also, the blank page may be interferrence from your web host. When I view the source of the register.php page I see:
Code:
<!-- www.000webhost.com Analytics Code -->
<script type="text/javascript" src="http://analytics.hosting24.com/count.php"></script>
<noscript><a href="http://www.hosting24.com/"><img src="http://analytics.hosting24.com/count.php" alt="web hosting" /></a></noscript>
<!-- End Of Code -->
That could be interfering with something.
Also, make sure you restored the users table to the default as it was when you first installed as any changes to the users table would make user registration not work.
Brandon