Two things can cause an error when uploading a file. The file is to large and times out or the file name is not formated correctly.

The maximum file size that can be uloaded through the file manager is 10 mb. The upload must also be completed in 10 minutes or you will receive an error.

It is also important to name your files correctly before uploading them. Files that contain punctuation or other "illegal" characters will not be allowed to upload, or will return an error.

It's best to name your file a solid string of text without comas, apostrophes, quotation marks, ampersands and other punctuation.

For example - That's a filename.pdf should be ThatsaFileName.pdf. The link or description for the file can be anything you want depending on the module, the file name itself is what is important.