I have a news & weather widget on my Nexus S home screen, set to show the weather for my current location. In its settings, I have it set to update once an hour along with automatic location tracking. Neither of these things work anymore since about a month ago (possibly the 2.3.4 update?). I have background data enabled, sync enabled, and I don't have any battery saver style programs.
I solved this myself after trying a few things. I deleted the News & Weather app's data by going to Settings>Applications>Manage Applications>All, Tapping "News & Weather", and then "Clear Data". I needed to delete and re-add the widget and set my refresh settings again, but now it works.
All you have to do is free up your internal memory. Many apps stop working if your internal memory is near full or has reached a certain storage limit. Move vidoes and apps go your sd card and it will start working fine