I just reflashed my n900 and started to have this problem. All new messages stay as unread. The conversations desktop app will remove the text when the message is read but the icon with the number of texts stays on the widget. The widget had this behavior for 2 different versions of the app. Text on names in conversations list stay colored even after deleting the conversations and staring new ones. I think its just an error in the reflash so.. I'm flashing it again.