[Brandon_R]

Maybe the email variable is conflicting with another variable that vBulletin uses. Try adding this plugin in the register_start hook.

$refferalemail = $vbulletin->input->clean_gpc('g', 'refferalemail', TYPE_STR);

And replace the email input fields with

				<tr>
					<td>
						$vbphrase[email_address]:<br />
						<input type="text" class="bginput" name="email" size="25" maxlength="50" value="$refferalemail" dir="ltr" />
					</td>
					<td>
						$vbphrase[confirm_email_address]:<br />
						<input type="text" class="bginput" name="emailconfirm" size="25" maxlength="50" value="$refferalemail" dir="ltr" />
					</td>
				</tr>

And the form action with

action="register.php?do=register&refferalemail=$refferalemail"