There appears to be a bug in iTunes 8.1 (50) that I haven’t seen reported anywhere on the net.

If you go to Podcast and have a column that shows the description field, there should be a little (i) button to show more info. Clicking on that button pops up the description in a window so large that it fills the screen. The OK and cancel button as well as the close window buttons are off the screen. Cmd-W does not close the window, and the window is set to be in front of the iTunes main window. 

Hopefully this will get fixed soon.

Here’s an image of the unclosable popup.