Cannot open File with new InDesign

A document created with new InDesign CS5.5 is not opening with earlier versions of InDesign. If I try to open in InDesign CS5 we will get an error ‘Cannot open “filename.indd”.

Cannot Open File
Cannot open "IDCSS.indd". Please
upgrade your plug-ins to their latest
versions, or upgrade to the latest
version of Adobe InDesign.
