I asked this on the Linux Mint forum but haven't heard back:
When I minimize a window - whether it is a file manager or whether it is an application such as firefox - the window will CLOSE instead of being minimized to the panel / system tray.
If I go to the terminal and and enter top I can see that the application is still listed (it still has a PID as well as a CPU% and a %MEM), but the window is no where to be found.
If I restart the application from the menu, it DOESN'T bring up the other window. For example: If I come to webmasterworld.com and minimize the window, then go to the Menu -> Internet -> Firefox, it will launch a new browser with the default home page (not the webmasterworld.com page I was just browsing).