Zip/compress it then upload it and you should be fine.

Use whatever your operating system has, or if you can't find that, download and install 7zip, it's excellent.

(forum category changed to help:authors)

Most files can be uploaded using the image uploader.

I've never tried to upload a script, but I'm assuming the "error" is an anti-hacking measure.

You could upload the script file to some other site (Dropbox?) and link to it.