added a conditional for $this->port in the mysqli driver.  Apparently it doesn't like being sent an empty string.
diff --git a/system/database/drivers/mysqli/mysqli_driver.php b/system/database/drivers/mysqli/mysqli_driver.php
index 4bbe5eb..f72db64 100644
--- a/system/database/drivers/mysqli/mysqli_driver.php
+++ b/system/database/drivers/mysqli/mysqli_driver.php
@@ -60,7 +60,15 @@
 	 */	

 	function db_connect()

 	{

-		return @mysqli_connect($this->hostname, $this->username, $this->password, $this->database, $this->port);

+		if ($this->port != '')

+		{

+			return @mysqli_connect($this->hostname, $this->username, $this->password, $this->database, $this->port);			

+		}

+		else

+		{

+			return @mysqli_connect($this->hostname, $this->username, $this->password, $this->database);

+		}

+

 	}

 

 	// --------------------------------------------------------------------

diff --git a/user_guide/changelog.html b/user_guide/changelog.html
index 03ff728..b7c84bc 100644
--- a/user_guide/changelog.html
+++ b/user_guide/changelog.html
@@ -61,6 +61,10 @@
 <p>Release Date: not yet released<br />

 SVN Revision: </p>

 

+<h3>Bug fixes for 1.7.1</h3>

+<ul>

+	<li>Fixed a bug in the MySQLi driver when no port is specified</li>

+</ul>

 

 

 <h2>Version 1.7</h2>