When I ungroup a conversation window, it simply disappears. I mean, the tab is not displayed in the tabbed conversation window, but the window is not separately displayed on the screen. It is just as if I had closed it. However, I can't open a conversation window with that contact, until I sign in again.
Actually, I found a way to display the window again: when double-clicking the nickname of the contact in the contact window, his conversation window is supossed to be displayed on top (although it does not). Then I press Esc or ALT+F4, and I can open the window again and it is displayed correctly.
One more thing: when i ungroup the window and there were only 2 windows tabbed, the one that doesn't disappear still shows a single, wide tab (see screen capture).
I use MSN Messenger 7.5 + Plus! 3.60 + StuffPlug 2.2 (BETA)