Complete loss of data in file doing this:-

Open a file with multi layer content.
Delete a layer (in my case this happened without any 'are you sure' checks, a bug in itself?)
Attempt to save the file.
An error message reports disk full or no permission. (disk not full and I logged on as normal)
Close QCAD beta3
Open QCAD beta 3 and attempt to load file. Error message reports no permission or unrecognised format.
Close QCAD beta 3

Open QCAD 2.2 and load file.
File loads ok but has default layer (0) only and no content.
Using Ubuntu 'Properties' file is reported as having a size of zero bytes.