from diggChris here at work just found this cool bug on all our Dell Optiplex GX520. It was so cool in fact that we decided to capture a video and post it online.
The bug appears when you put your mobile phone close to the cd-rom unit of the dell and then recieve a sms/txt.
What happends is it goes into some sort of suspension mode from which you can't bring it back without breaking power or holding down the power button for four seconds.
It worked with all the new dells here in the office and with any mobile phone. Just make sure to save all of your work before you try it at home.
The only remaining question is: Is it a bug or feature?