I am running a relatively new Windows 7 64-bit computer. For no apparent reason I've begun getting logonui.exe errors that claim there's a missing userdata.dll file. This occurs whenever I shut down and boot up the computer. The shut down or boot up processes hang until I acknowledge the message, though once I'm past it there does not appear to be an lingering effect. Where does this message come from, and how can I get rid of it?