This appears to be a folder corruption on the hard disk. Normally I would recommend opening WX5, selecting backup and redo but not all files are backed up and I believe library.xml is one of those.

Assuming you have an iwzip file of the project you can import this and it will resolve the problem (this will NOT overwrite the existing project).

If you do not have an iwzip file you have a number of options, ensure the system has been recently restarted, ensure the WX5 project folders are on a local drive, ensure the WX5 project folders are not shared or synchronised by any backup or cloud service and if all else fails you could attempt to repair your files by running chkdsk c: /r (good luck and please advise your progress)

I make project backup on 3 places including Cloud... So i restore the backup day before... I'm courious why this error is apeared...

Hello Croatia

Sometimes, this error can appear when something went wrong while saving the files.

When this happens, check your project folder. You might find some files named xxx.xml_tmp

If you do, simply replace the old files with the _tmp version and the project should start working again

Keep me posted on this here

Thank you

Stefano