Fatal Error with spl_autoload()

Having just installed this Template over Magento v1.5 I get

"Fatal error: spl_autoload() [<a href=’function.spl-autoload’>function.spl-autoload</a>]: Class Zend_Log_Exception could not be loaded in /domains/.com/http/lib/Zend/Log/Writer/Stream.php on line 132"

This error is causing magento to look for a method or class that hasn’t been loaded and causing the system to run into an endless loop.
My exception.log runs into several Gbytes as the error outputs to the log file.

I first noticed this when navigating the site. On add to cart, the site just reports Shopping Cart empty.
If I try to log in I am not taken to the user page but remains on th log in screen.
The error in question can best be seen while using the search box at the top of the screen.

If I revert the site to an older template this problem doesn’t exist.
At the moment I can’t tell if this is a template issue or my Magento install.

If anyone has any thoughts I would be greatful.

regards Tony