sounds like you have some other process managing the files in that folder.

did you setup the folder as a "Secure" file folder? if so, the DNN core file system will rename all the files for you adding a secure extension to each file making sure you can't browse directly to the file. There is a file 'synchronization' scheduler task the sync's your files and will rename them, which it sounds like is what is happening to you. The Repository module stores the filename and location in it's own table which is why the files show up in the module. The Repository only goes back to the folder when it's time to download a file, and since that filename has been changed, it can't find it.

If this is happening, you'll need to change that folder back to a normal file folder. The Repository module protects your files by inserting a Guid between the filename and the extension, then strips it out when downloading to get back to the original filename, it won't work if you are storing your repository files in a 'secure' folder.

glad you figured it out!!