Error message: "An exception occurred during the backup process."
I googled it. But if i don't find an answer after 5 pages I give up.
Anyway, I wasn't even sure if i can just import a backup file done on a MAC into a PC. Couldn't find an answer for this as well.
Then I tried with exporting "My collection" as .GBD and .GPX file and importing that to the PC. Got all the data but I lost the file structure and no birdseye images were imported.
In the end I managed to get the data the way I want on the PC as described before. Took just ten minutes.
To sync would be nice, but I can live without it. I'll just replace the files before I go for the ride.