"Navigation" window doesn't appear
 

"Upgrade to pro" window, "Preference" window, "Statistics" window appear,
but "Navigation" window never appear.
I cannot see Navigation window, so I cannot do anything.

I feel, since I have upgraded itunes 3 to itunes 4,
this trouble happen to my computer.

I use: LimeWire 3.6.15
Mac OS X 10.1.5
384M
Power PC G3
iTunes 4 (Japanese)

Would you tell me how to fix this problem?