Fixing Minimized Window Issue
It can happen that upon logging in, when you select a character, the client window disappears - but the client is still visible in the Taskbar. If you have sound enabled, you can still hear sounds from the game, but there is nothing to see.
This is because Windows Operating System remembers the location of your client window on the screen (based on the title of the window). When you select your character, the client window is moved to its previous location on the screen, and that location may be outside of your actual screen. This can happen after reconfiguring your display settings in Windows (removing a display, changing positions of displays), or sometimes just randomly on its own.
(applies to Windows 7 and newer)
1. Hover your mouse over the "Ultima Online - <Character name>" tile on the taskbar.
2. A miniature preview of the game window will be displayed above the taskbar tile.
3. Right-click on the miniature preview window, and select either "Maximize" or "Restore".
4. After the window comes into view, be sure to resize it, and drag it, so that it fits well into the screen
5. That should do it - but for windows to remember the current position of the screen, it's recommended that you restart the client.