Why does Itunes "stick" on the Itunes Store now?

Using a Mac, I habitually use the cmd- keystroke to cycle through windows within an application. I've been doing this for years on every application, including Itunes. Recently, though, I've noticed that in Itunes, if I cycle to the Itunes Store window, cmd- stops working. I can’t get to another window without using the menu or just closing the Itunes Store window.

What gives?

Works for me.
What version of iTunes and OS?

Itunes 9.0.3, Mac OS 10.5.8

That’s exactly what I’m running on this machine. I just tried it with the equalizer window open and iTunes on the iTunes store, and it worked. What windows do you have open?

It happens no matter what combination I have open, but usually, it includes Itunes, Itunes Store, and one or more of the following open in separate windows: Podcasts, Movies, TV Shows, Downloads

Seems to work OK for me.
Sounds like cmd-` got redefined for your version of iTunes. Are you running any hotkey apps?