It seems like you are uploading to a BSD server with Pure-ftpd as your FTP server. It is possible that your FTP server does not support certain characters that are part of the JPEG snap's file name. If this is the case, you can set WebCam Monitor to append numbers instead of date and time. These types of file names should be supported by any FTP server. To know the file that WebCam Monitor is currently uploading, you can view the Upload Status from the View menu. This option is available in the latest version of WebCam Monitor. It may also help to clear the entire upload list before you start monitoring.