Windows 7 always hang explorer,rgd tsk mgr priority

Dear all,

Recent my windows 7 always hang, i not sure what happen, I check my Event List, nothing special there.

When the OS start hang, only mouse can move, I use Ctrl+Shift+Esc or Ctrl+Alt+Del also no response. One funny thing is when I press Windows+Tab, it got response. Hence I conclude that, the Windows+tab key priority would be higher than Ctrl+Shift+Esc or Ctrl+Alt+Del, it is quite funny right? I really no idea what is this improvement for...

After a while (properly 3-5minutes waiting, normally I press reset button would be more faster than wait), the windows response super fast, execute what I press b4 like Ctrl+Shift+Esc many time, it will come out task manager and I press b4 Ctrl+R, The Run Command will execute at the same time.

Where can I check what's going on?

I am sure my keyboard working normally, because of windows hang, I cant do anything.

Just want to ask anyidea why windows make Windows+Tab higher priority than Ctrl+Shift+Esc or Ctrl+Alt+Del, supportly Ctrl+Shift+Esc or Ctrl+Alt+Del should be have the highest priority.

thx for your reply, I know that because my explorer.exe unable to click, what I can do is just use Windows+Tab switching around the windows, I can't right click, and what I can do is just wait until explorer got response.
I am wonder, why Windows+Tab able to work, but not Ctrl+Shift+Esc or Ctrl+Alt+Del. Last time during XP, anything happen, Ctrl+Shift+Esc or Ctrl+Alt+Del is the top priority, at least I can end task for explorer.exe, and start again, but Windows 7 I unable to do that.

yup, the mouse is working normally, I think because of explorer.exe, i can't do much thing other than Windows+Tab views the fancy windows slideshow.