I love WB and have many hosted domains using it

Over the weekend I needed to change the hard drive in one of the webservers. For the WB installs I backed up the databases and the web directories. The only thing that changed was the hard drive. OS is still CENTOS 5.3, PHP is the same, as well as apache and MYSQL.
Now when I create the website, copy back all the webdata and restore the MYSQL database (being sure to update the config.php file) all I receive is a blank page - no errors, just a blank page....when I browse to the site.
I tried doing an install of WB first and then copying over the top, but the result is the same...
I have checked the MYSQL database for errors and it is clean.
Any help, greatly appreciated.. I am using 2.7
Thanks
Matt
P.S. Just wanted to add that we have many sites on this web server (some use another popular CMS). I followed the same process for these and they worked fine..