[Klaus]

I have fiddled around with the Mobile Documents folder in the ≈/Library.

First, I moved Word .doc files from the Documents folder to the Documents folder within the iCloud com~apple~Pages folder. These files could be opened with Word.
Then I moved the .doc files to the com~apple~Preview folder, and now I was not able to open them in Word; when moved to the desktop Word still couldn't open the files. The error message was in both cases: Word cannot open this document. The document might be in use, the document might not be a valid Word document, or the file name might contain invalid characters (for example, \ /).

Furthermore, they also cannot be moved any longer - resulting in this error message: Items can't be copied to "destination" because you don't have permission to read them. However, permissions are set correctly judged from the Get Info window, and running Repair Disk Permissions from the Disk Utility doesn't correct the problem.

It seems that iCloud have tagged the files, so that there is no longer permission to open them with the original creator application. Pages also fails to open them with the message: "Import Error. The file format is invalid". Trying to open them with Preview crashes the program.

Re-installment of Mountain Lion hasn't worked.

What has happened, and how can this problem be solved?

Tampering with the Mobile Documents folder appears to be dangerous, as it may lead to irreversibly(?) damaged files!

KB, Copenhagen, Denmark