Getting unexpected error map layer

[DeanGross]

i am trying to pick a basesmap for the webpart and i'm getting "Unexpected Error Map Layers have not been instantiated. What does this mean and how can i fix ?
TIA
Dean

I just found out that this was occurring because i had not gone into the Edit mode for the web part. This is a pretty ugly error message for this event.

[KatherineDalton]

Hi Dean,

You should be able to switch basemaps without being in edit mode, so it sounds as if something else might be going on. I checked with our Dev team, and we aren't doing anything different in edit mode; we just load additional functionality. 

A few questions:
-Are you using the default (out of the box) basemaps or a custom basemap that has been added/ configured in the ArcGIS Mapping Basemaps list?
-Are there other layers in the map besides the basemap that might be causing the issue? One way to isolate the issue is to insert a brand new map web part (no other layers whatsoeverr), save the page, change basemaps, and then verify there are no errors both in runtime and edit mode.
-Does this exception occur every single time you try changing basemaps?

If you can get back to us, that would be very helpful.

Thank you,
Katy