I've been having the same problem on Windows 7 32bit Windows 7 Home Premium on a Dell 5150.
After no keybord input to the PC for 10 minutes or more it is totally unresponsive except for the mouse pointer which moves around as normal. If I double click on a folder, or try to open a program, or hit CTRL ALT DEL, nothing happens for up to 3 minutes - then the action opens as normal. I looked for a fault report and "somewhere" is saw many reports that said the driver
for my ATI X800 video card had failed to respond for 10526ms i.e. over 10 seconds. Although my delays were a lot longer than 10 seconds I was suspicious of the video card as it has an out of date driver as there are no Windows 7 drivers
available for it. I have now replaced my video card with a Geforce 9500GT with Win 7 drivers and the problem has gone.
There is another possible solution and Hotfix for it - maybe worth trying:
see The desktop stops responding for some time after you resume the display on a computer that is running Windows 7
ps: I got this tip from the Windows Secrets Forum at Microsoft Windows XP, Vista, 7, Internet Explorer (IE), Firefox, Windows Update
there's some very interesting information there.
I haven't tried the hotfix as my problem has gone away, although I have had just one freeze yesterday for a few seconds. I'll be interested to see if anyone has tried this hotfix.