trekkingnut changed the 'Thread Display Mode' to 'Linear - Newest First'.
That would drive me completely nuts, because you'd have to scroll down to find your place and read 'up' instead of down. I second Frawg's suggestions instead.
I always click the 'New Posts' button to get a list of all the threads with fresh activity. Then, I click the 'Go to first new post' button (
) beside each thread that I want to view from that list, and have each one open in a new 'tab'. Then, I just read through each tab.
When I'm done, if I haven't read every thread with new posts, I make sure to use the 'Mark All Read' function so that the 'New Posts' option is fresh when I come back.
<- Is really the best way to skip to the newest posts you haven't read.