I came across this when a customer called in and had this issue which was not showing up in earlier versions. The User had embedded Images using Raster Design and never had this issue before. the Images are there and shown and everything functions properly, however every time they open the DWG this error comes up. You can select the "Always Ignore Unresolved References" option on the Error Message. however then you will not get this warning but you can still see the missing references if there are some in the Reference Palette.
This has been submitted to Autodesk and verified as a bug and has been submitted by Autodesk to Development to be corrected.
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