In the php.ini file used by the PHP5 executable, the include path is hosed. If you installed in the default location and are running Windows, you'll probably find the file at: C:Program FilesZendZendStudio-5.5.0binphp5php.ini

The problem is that the value of include_path isn't wrapped in quotes, making portions of it act like a comment and "hose" your directory path. Thankfully, it's a pretty simple fix - just quote the value and be on your merry way. It's one of those bugs that has the potential to be so small that it'd be very frustrating to find.