Happened to me too, but not over my normal DSL IP, but while browsing through Tor. As you note, one CAPTCHA is replaced by another seemingly without end. I gave up after 3 or so tries and switched to DDG, which is what I use when browsing over Tor. It's Google's loss, certainly not mine.

Which shows how important it is for Internet health that we have search competitors to Google who maintain their own indexes. No one company should become the sole practical gateway to the Net.