First, the popup commes if a file is open on the local computer and another person have uploaded a new'er version of the file.
The system is trying to replace the old version on the local computer and the file is locked.
Just follow the instructions displayed on the popup (close and/or save the file currently open, and the popup will disappear and the new version is ready)
If this is not the case, it's normally do to the following:
1. The filename has illigal char in it. On MAC it's ok to have ":" or similar in the file name, but not on Windows. Please rename via the file via webclient, removing the illigal char.
2. The sharename or one of the folders in the path has a blank Space at the end. This Again is ok on web/MAC but not on Windows. Use the webclient to rename the share/folders that have the blank Space at the end.