Make sure assets and _combinedfiles inside assets is writable by the webserver.

This error indicates that certainly isn't right, something weird is clogging up the system. Flush your manifest with /dev/build?flush=all (or go manually delete all cache folders for SS), and run /dev/tests/.

Also do what Sean said.

Do you see anything additional if you add ?debug=1 instead of ?isDev=1?

Keep going with a full reinstall from scratch. Something is not right with your copy of the code and your webserver/PHP installation, the installer will walk through all aspects of your environment and correct/identify it.

To lurkers, this is NOT typical.

Cool, I can say that the error that is being thrown is in the core Controller class and that piece of code is pretty robust. Not having any controllers on the stack is plain bizarre, and seemingly impossible as that function can't be called until a controller is pushed on the stack.

Sometimes its easier to stop troubleshooting and start over... Good luck!