Re: 169.04, same Composite + offscreen Xid issue
Let me rephrase what I said.
Most of the times that I've seen Xid errors it has been due to physical hardware problems (the cards ended up dying). However, the most recent time it was due to a driver bug (the Xv bug). The 169.04 driver fixed an Xv bug with non-Turbocache cards. Perhaps you have a new case of an Xv bug that nVidia is not familiar with yet.
Search this forum for nVidia's official explanation of an Xid error. This has been brought up countless times. It even started a huge thread where people started calling each other names. Don't let this thread become the same thing.