We had an issue with documents in a Folder within a Document library. We renamed the folder and the Modified date of all documents updated to be the date at which the folder was modified - which for us caused some strange results as the last user to modify the document had left the company!
Anyway Service Pack 1 appears to fix this, I had no problems applying this to my environment - instructions are here: http://blogs.msdn.com/sharepoint/archive/2007/12/11/announcing-the-release-of-wss-3-0-sp1-and-office-sharepoint-server-2007-sp1.aspx