Some changes in the config files require umbraco to recalculate the url's for the nodes. Sounds like that's what happened.
Simply right-click on the top-level nodes of your site in the content section of umbraco, and select the "publish" menu item. Be sure to put a checkmark in the "publish children" box.
Repeat for all the top-level nodes so that all the nodes will get republished.
Note that this is not the same thing as right clicking on the CONTENT node and selecting "republish entire site", which won't recalculate the urls.
cheers,
doug.
MVP 2007-2009 - Official Umbraco Trainer for North America -
Percipient Studios