Our marketing department is using Word 2007 to post articles on a SharePoint 2007 blog. Today, a weird issue came up: when you select a category from the drop-down list, that category was created on the SharePoint blog every time, no matter if it existed already or not. This results in duplicate categories in the SharePoint blog.
The solution to this problem is very simple: on the SharePoint site, check the Categories list for items that have a space at the end. If an item in the category list has a space, it gets recreated again when you select the category in Word.