In lucid, running kernel 2.6.32-16-generic (on Asus Eee 1005HA) I don't get this bug anymore. However, as Ron Bentley described, I too can't run compiz when the external screen is set side-by-side. If compiz is running before I plug in the external monitor, it closes, and starts metacity as a fallback. When setting the external screen to be above or below the internal screen, compiz continues to run, without switching to metacity.
In lucid, running kernel 2.6.32-16-generic (on Asus Eee 1005HA) I don't get this bug anymore. However, as Ron Bentley described, I too can't run compiz when the external screen is set side-by-side. If compiz is running before I plug in the external monitor, it closes, and starts metacity as a fallback. When setting the external screen to be above or below the internal screen, compiz continues to run, without switching to metacity.