I'm not sure of how you mean to handle illegal file names across platforms, but I would suggest that if a mac folder ends in a space that you don't sync that folder to a windows computer... After having issues in the windows sync folder, I had the mac use make a "test " folder and it synced. I had to delete the folder from the command line with the unc path. I've not had the time to try making other folder/file names on the mac that would be illegal in windows, but I hope you already take care of illegal names and this just slipped by. 1.4.103 on the pc side not sure on mac version -Michael edit: How the end user can deal with the directories with spaces at the end If you have the same issue and need to delete the folders in windows, I found going to an administrator command prompt and typing the following works. replace the c:\direcory\directory with whatever your folder name really is. Make sure it's empty first. Note there is a space before the second quotation mark. rd "\\?\c:\directory\directorywithspaceatend " If you end up with c:\direcorywithspaceatend and c:\direcory, you'll have to delete the one without the space first from the command prompt. I've now seen that if you have both that the files disspear from the one with the space. But if you delete the one without the space that files reappear in the one with the space so that you can move the files out and then delete the one with the space. What a mess!