If you doubleclick the gray area under the jumps/files/web/debug tabs so you get a floating window and then close this window the IDE locks up, you can't even open the menus any more. You can however close down the IDE by right-clicking the taskbar button.
Huh!? When you double-click it, it's simply undocking. Works for me. What OS?
Undocking works but try closing it.
Windows XP SP3 but it was like this from start and then I was using XP SP2
Hmm, now I can close and open the sidebar without troubles, interesting. Yesterday I couldn't access GL-Basic at all after closing the sidebar but I guess a reboot solved that. I have had this earlier too so I just never touched the sidebar because I lost the code I was working on a few times :-)