What you're seeing is a freeze or crash of the program that manages your taskbar - this is a common Windows problem when you leave your computer on for a very long time. Adding RAM or running fewer programs may allow you to go longer, but Windows will pretty much always do this eventually if you leave it running long enough.
To get the taskbar back:
1) close any open folder windows
2) press ctrl + shift + esc to open task manager
3) go to "processes" tab, if you find any "explorer.exe" in the listing select it and "end task"
4) click file, new task, type "explorer" and hit ok.
There is one major problem with this. WinMX, FXServer, RoboMX, Metis, and BideBotMX will lose their system tray icons. I haven't tested the new WCS so I don't know if it will or not, and other programs may be affected as well. Basically this is because some programs don't make their system tray icon the way they're supposed to. This mainly affects MX-related programs (most programs get it right). There are two possible ways not to lose these programs:
1) don't minimize these programs to the system tray
2) use a program like "PSTrayFactory" which can detect when programs make their system tray icons and ensure they get added properly