Are you trying it from a phone or iPad? I get those errors sometimes on my iPhone or iPad when I try to upload a file that I know fits the requirements. And then all of a sudden, it will upload.The forums keep saying that there is an error when I try to upload a file (tried many different files in different posts) the error says "There was an error uploading your file". I tried many times since yesterday with different files and on different posts including this post.
It would help to know what sort of files you are trying to upload, only certain file extensions are accepted. There is also a size limit per file.