I was typing simple one word keywords like "dogs, money,cars etc.." I may have tried one of them twice, and maybe that triggered it
Its over now, it only lasted an hour or so, then it let me type in some verification code But then i tried it again just to see what happend, and sure enough. i got it again
yeah try it if you like, just google "dogs", then google "dogs" again, try it a few more times, and you'll see the message
I get this when I'm studying the serps real hard, trying to find my sites for 1 word key words, go through the 100 pages of results and then click to get the sups and go through the 100 pages again. I always feel like this indicates I am studying the serps hard enough when I get this and am sort of proud of it
Happen to me couple months back seem to be they are having a lot resource drain on their server from spyware and viruses
Is it possible you were searching for something which includes the keyword "forum" I have seen such message on queries involving "forum"
this is a measure that google had to implement to prevent bots from copying loads of pages with results and to prevent web based worms that use google to find vulnerable hosts. However some times google will suspect innocent queries but it's rare. Better safe than sorry.
I got flagged when I has a SEO toolbar installed- one of those that tells me all the stats of the site on the results. I really stopped being able to query more than a few times an hour. Uninstalled the toolbar and everything worked again.