A couple days ago, many users started complaining that Google Images's next button didn't work. It basically showed the searchers the first page results, even though they clicked on the next page button.
There were literally dozens of complaints about this in the forums. Google finally tracked it down and posted in one of the Google Web Search Help threads that it has been fixed.
Jaime from Google said:
As it turns out, this was indeed a problem on our end. We have a fix and I believe it should be completely rolled out by now. If you're still having this problem, try clearing your cahce once more. If it's not cleared up after that, let me know.
Glad it is fixed, because people were beginning to think they were going mad.
Forum discussion at Google Web Search Help.