I'm currently working on Views 6.x-2.16. I very frequently get the following fatal error when clearing caches:
PHP Fatal error: view::destroy() [<a href='view.destroy'>view.destroy</a>]: The script tried to execute a method or access a property of an incomplete object. Please ensure that the class definition "views_plugin_display_default" of the object you are trying to operate on was loaded _before_ unserialize() gets called or provide a __autoload() function to load the class definition in obfuscated/views/includes/view.inc on line 1611
I suspect that this is due to an incompatibility with autoload. Some how, views attempts to destroy a view object that has an incomplete handler. A simple change to the destroy() method prevents this. Patch forthcoming.