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.