Hello,
I just bought my 2.53Ghz 15 inch Macbook Pro 3 days ago and I've had this problem too. But, for me at least, the problem does not happen after switching Spaces... It'll often do it randomly 2 or 3 times a day when I'm not even running any significantly hefty applications and have not switched spaces for probably 2 to 3 hours. And although it's not happening immediately after switching Spaces, the problem did begin to happen when I enabled Spaces 2 days ago, not sure if I have the same problem as everyone else or not, because my system becomes slow, laggy, and borderline unresponsive, one time resulting in a forced hard reset.
And I did just try what the gentleman on the former page said about downloading Things then hitting Ctrl
AltSpace, click cancel on the pop up then switch spaces, and the keyboard did become unresponsive.
I just switched over from PC and I consider myself to be pretty knowledgeable and capable computer user but with my little prior experience of OSX I'm sort of helpless.
I just went ahead and disabled spaces altogether, I just did it so I don't know if it'll help or not.
Here are a list of programs that are pretty much always running on my Mac, I don't think it's 3rd party app related, but just for kicks and giggles I'll go ahead and throw it in there.
Mozilla Thunderbird,
Safari,
iTunes
Growl (Growltunes, Growlsafari etc)
Bowtie
Quicksilver
Cinch (Couldn't live without my Windows 7 Snap to full screen perk)
Last.fm scrobbler
Avast (Antivirus on a Mac... That's the old PC user coming out in me 😉 haha)
I hope this gets fixed soon! I haven't had any other complaints about my switch to Mac other than this one problem.. Well that and you Mac users are HUGE fans of insanely complex keyboard shortcuts, but I guess I'll have to get used to it. 🙂