Setting Forum Display Options

Several of the forums display in what I call 'normal' mode - last post, last month, decending. However, I can change the display mode for the general IT discussions, but i can't save the settings. I have looked through the FAQ and no help.:( Any tips?

User CP > Edit options >go to "thread display options" > last choice in that box is "Default Age cutoff". Choose another option in the radio box, such as "Show threads from last 45 days" > "Save changes" (at bottom.)