Dell is still investigating the "flaming notebook", here's what they write about it on a blog:
We replaced the customer’s computer and are still investigating the cause. We think it was a fault in a lithium ion battery cell. Dell's engineering teams are working with the Consumer Product Safety Commission and a third-party failure analysis lab to determine the root cause of this failure and to ensure we take all appropriate measures to help prevent a recurrence. By the way, lithium ion batteries are used in billions of notebooks, mp3 players, PDAs and cell phones these days
