This information also relates to the error An unknown PNG error has occured.
Please try recovering the file using the ExpandXar exe available from here
If this does not recover the file, then please submit a support ticket and include the following information:
1. The full error message
2. The exact version of the program you are using ( Select Help > About)
3. Include the Xar file as an attachment
4. Let us know you have tried using ExpandXar.exe to resolve the problem.
We cannot guarantee that we will be able to recover the file. However submitting the problem file will enable us to review the file and try and determine the cause of the error.
We recommend you save your files regularly.
All our Designer products has an auto backup feature enabled by default, which will create a backup your open files every 10 minutes (or whenever the program is idle thereafter for this to occur).