When you add a movie—or a batch of movies—to Usher, Usher needs to process them. You'll see this activity indicated by a small progress bar in the lower right corner of Usher's interface.

What exactly is processing doing? Basically, Usher needs to get a preview image for each movie, as well as find the movie's total time. This process is called 'crawling,' and depending on the movies you're adding, it can take a while. (If you notice a process in Activity Monitor named ushercrawler, that's the background process that does the crawling.)

Usher uses QuickTime to do its processing, so it works best with movies that are in a native QuickTime format.

If you're working with certain movies that need the Perian or Flip4Mac WMV QuickTime plug-ins, you may find that crawling can be particularly slow (and CPU intensive). If you have a huge batch of such movies to process, you may wish to break them into smaller bundles.