I was seeing the "Error loading NvQTwk" message every time I rebooted my computer.
To solve it, I clicked the Start button, then Run. In the space I typed msconfig and clicked OK.
On the General tab, I clicked Selective Startup instead of Normal Startup. On the Startup tab, I unchecked the box next to NvCplDaemon. (This file was still trying to launch even though I'd uninstalled the Nvidia drivers as thoroughly as possible.)
Then I clicked OK, rebooted my computer, and the error message did not come back.