The ubuntu icon in the top left is missing in unity 2d.
any ideas how to get it to appear.
this is on my other pc running nvidia 6150se / nforce 430 gpu which doesn't work very well with unity 3d.
Did you change the theme with the Appearance manager?
If you changed it, try to change it back to the standard theme.
If it really has to do with your GPU, I'd install "Additional Drivers".
Unity isn't stable yet, so that could also be a bug, if nothing of these suggestions worked, please create a bug report: https://bugs.launchpad.net/unity
I hope this helped you, Daniel