Pages won't open document

We are getting an increased number of users all with files that refuse to open in Pages 5, particularly Pages 5.1.

I have gone over several of them and been unable to correct the problem, only able to open the Document.iwa sub file in the package to look at the mix of text snippets and I presume .xml.

Apple reportedly has also examined these and been unable to rectify them.

To aid some kind of resolution I ask that users who have had the problem post here, detailing the last things they did with the file and whether there is anything particular to the files that may be leading to the problem.

Particularly relevant would be where and how the files were last saved.

Are they being transferred or backed up to iCloud?

Are you using 3rd party syching or backup solutions like DropBox?

Are they being re-edited on iDevices, iWork for iCloud beta or back and forth from Word .doc?

Were there any preceeding warnings or difficulties of any kind with the document?

Or anything else you can think of.

Thank you,

Peter