Comment 29 for bug 973506

With high X CPU bugs, *typically* the cause ends up being a client program rather than X. The reason is that X is just a server and its load is driven by client requests. So if some client is stuck in a loop making X calls, that can show up as high CPU on the X process.

However, with nvidia who knows. It's rare but not unknown for there to be driver bugs that cause high CPU on X.

As a general rule, with bugs against nvidia, unless it's a packaging issue or something that quite definitely is wrong on the Ubuntu side, or something you already know is fixed in a newer driver version, the bugs should be reported upstream at the nvidia forums.