Minimized application disappears due to shell registration.

Cause:

The application's shell registration was not forwarded to Windows. If one application has this problem, it can prevent other applications from minimizing to the Taskbar as well.

Solution:

Use ALT+TAB to cycle to the desired application.

NOTE: Some applications do not display an icon on the Taskbar when running. This is not a Windows 95 error but the result of a non-standard application characteristic. Although the minimized icon is not visible, the application can still be accessed.
Press and hold ALT down while pressing TAB repeatedly to cycle through the running applications.