You mean you can see poser in taskbar but can't get the window open on desktop, but you can see the library window?

I had struggle with this too. Closing poser from taskbar while it's minimized and next time you start it you can't get the main window open.

Try
-Select poser main window (not library) from task bar
-Press alt-key
-Navigate with arrow keys thru the menus (the dropdowns show up on top left corner of screen) and find the window menu and choose maximize.

Atleast this way I can restore the window without messing with preferences.