Several non-GIS users in my office rely on ArcReader to do their jobs. This morning a few of these ArcReader users informed me that when they turned on the ESRI image base map that I included in the .pmf a window would pop up asking them to log into a GIS server. This happened to several people on several different computers (but all using the same .pmf on a network) at different times. This didn't happen every time we tried to turn on the ESRI imagery, however it only happened when we tried to turn on the ESRI basemap. Has anyone experienced this problem before? If so, why does it happen and how can it be mitigated?