This issue is not issue to reproduce. I failed to do so following your description. I explain my configuration.
I'm using Windows XP x86 and Windows 7 x64. Both Windows are configured for using Windows Classic theme. The visual effects are set to optimal performance (no window animations, no shadows, ...). I don't use ClearType. I have even disabled the color fading of the window title bars by setting for color 2 the same color as for first color. So the windows look on my computers like in Windows 95 which speeds up drawing them.
The Windows XP computer is older and from technical data much slower than the Windows 7 computer. But the Windows XP machine is totally optimized by me for best performance while I did not spent much time on Windows 7 computer to find out all unnecessary services running in background which could be disabled to make the machine faster. Therefore on Windows XP UltraEdit restores from minimized state to normal state instantly without any noticeable delay while on Windows 7 I can see some delays on restoring and redrawing the windows of UltraEdit.
I use in UltraEdit a customized theme based on the standard Classic theme with application style set to Windows Classic. Therefore also no graphic gadgets in UltraEdit itself. A fast GUI is for me much more important than a stylish look.
The file tabs are configured in UltraEdit for being not dockable and file tabs bar is set to scrollable single line. In other words on right clicking on any file tab and opening submenu
File Tabs in context menu, the first option
Dockable is not checked and the second option
Single Line - scrollable is selected.
The configuration settings
Files selected in Explorer will open in a new single instance,
Allow multiple instances and
Maintain separate process for each file opened from external application must be all unchecked at
Advanced - Configuration - Application Layout - Miscellaneous to make force re-opening already running instance of UltraEdit instead of opening a new instance on clicking the shortcut respectively activating it by Windows hotkey as I use, too.
I could not reproduce the issue on Windows XP at all. And I have never seen something similar on my Windows XP computer in the past.
I failed to reproduce this issue also on slower Windows 7 with your steps. I tried both states for setting
Minimize on system tray (not taskbar) at
Advanced - Configuration - Application Layout - Window State. I run more than 10 attempts on Windows 7 with both states for this setting using my configuration.
But I can nevertheless confirm that there is somewhere a problem on restoring UltraEdit as I have from time to time the problem that on using
ueFastStart to open 1 or more files from within Total Commander in already running instance of UltraEdit, the selected file(s) is(are) not opened in UltraEdit and the restored UltraEdit window looks similar to your screenshot. But whenever this problem occurs, switching back to TC with Alt+Tab, hitting hotkey for running ueFastStart a second time for the still selected file(s) always solves this problem.
So I could not yet find out under which conditions this display issue occurs in a reproducible way. This is the reason why I have not yet reported my observations to IDM support by email. As being myself a developer I know that an issue which cannot be reproduced with a step by step instruction and which occurs only randomly under unknown conditions is very, very hard to find in code if the reason can be find at all by the developer.
As this is a user-to-user forum, I suggest nevertheless to report this issue by email to IDM support if you can reproduce it at any time on your computer. Perhaps IDM support can reproduce it, too. You should add as much information about configuration of UltraEdit and Windows like I have done here.