This is an infrequent issue I've had, but it has happened more than once in the last few weeks that I've been using CS6 on a regular basis:
On occasion, my spacebar will just stop working in Illustrator CS6, so I can't use the hand tool or zoom or… you know, type, basically making Illustrator unuseable. Now, I'm PRETTY sure it has nothing to do with my actual keyboard, because the spacebar will continue to work just fine in every other application even after it does this.
The only fix is restarting the computer. Just restarting the application doesn't do it. Deleting the preferences file and restarting doesn't fix it. It's really perplexing.
Now, I'm NOT certain about this, but I think it might occur after waking from sleep (but not immediately, so perhaps it's unrelated). If/when it happens next, I will attempt to see if I can reproduce the issue, but so far I have no idea why it happens; it just seems random.
I'm using a late 2008 MacBook Pro with 8GB of RAM, running Mac OSX 10.7.4 and Illustrator CS6 (16.0.0, in case people see this after an update has been released).
In my case was an antivirus app called webroot
I was having this problem as well. I just decided to restart my machine and it fixed the problem. Hope this helps.
I just starting having this same recurring problem this month. I've been using Illustrator since 1993 (on both Mac and Windows platforms and various computers) and have never had this really annoying and stupid problem.
I simply had to quit Chrome and then the space-bar=hand-tool magically started working.
Thank you for commenting here. I had been problem-free for quite some time, but recently have experienced the problem again. I'd used CS6 (problem free) for a good while and finally moved* to CC 2015 in January. Was fine for awhile but the space bar issue reappeared just two or three weeks ago. I find that rebooting the system solves it, for awhile anyway, but what a pain! Next time it happens I'll quit Chrome ... and hope it works here, too.
* I do not consider 2015 an upgrade. A lateral move at best. I find it stunning that Illustrator is in its, like, 18th iteration and there's still loads of crap it can't do, or does clumsily, etc. But I digress.
Just curious: do you use webroot?
After exhaustive search and several rage outbursts, I've found out my antivirus was the problem. Here is the solution: