I had the same problem - the trial version worked well, then as soon as I bought the program, I got the same error - it would upload small files ok, but anything larger than 5MB it would time out partway into the upload, and give me the same "unable to change to the directory" message. I've found a workaround - instead of using the upload button for a specific file, use the Synchronize button instead. It will duplicate the whole folder from your machine into the FTP folder, but at least it gets the file that you want in there. In the future I'll create a new folder with only the file I need to upload in it, then use the Synchronize button. I have no idea why that should work instead of just uploading a single file, but I found this solution by chance and wanted to post it here. It's frustrating that there's no tech support on this forum, or support with the program - that's just sad. But hopefully this workaround will help a few of you. Good luck. Bill.