I use c2 in 3 PCs (notebook, desktop and Job's) and I have my project in my google drive folder so it syncs every time I turn on any PC. The problem is that Google Drive shows as ticked (synchronized) some files that aparently aren't and it looks like some files of the project (like the files indicated in the pop up) where still synchronizing when I tried to open the project.
When I press "Omit", another Pop up asked me for another missing file (an xml in this case). If I press on something I would translate as "Void", the program crashes.
Once the sync was finished, I tried to open the caproj and it worked fine.
Not sure if you need any other data.
bye and thanks again!