Some Google users are having technical issues with changing their search preferences.
The issue appears to happen when you have a default location set and then you try to change another setting. Google may pop up a warning that reads:
Sorry, the location [city, state] was not recognized. Please try another location.
The issue is, the user did not change his or her location. They only tried to change another setting, such as turning Google Instant off.
I personally cannot replicate the issue, so either it doesn't affect me or it was fixed already.