Unchecking the "Vari Bright" option in the ATI Catalyst Control Center resolved the issue for me as well. It seems this option dims the brightness of the display when unplugged; however, I believe Windows also does this (or, at least it does on my Dell
XPS 16). Perhaps two programs attempting to essentially do the same thing are the cause of the atibtmon issue?
162 people were helped by this reply
Did this solve your problem?
Sorry this didn't help.
Great! Thanks for marking this as the answer.
How satisfied are you with this reply?
Thanks for your feedback, it helps us improve the site.