Problems uploading zipped mp3-albums

I am trying to upload mp3-albums into my shop kcsoundshop.com. I have succeeded with a couple on my laptop, with one I had to use another computer to get it done. That one was also a laptop. Both are using wireless modems, which of course are slower than a physical connection. Now I don´t succeed at all. In previous cases I was timed out, now I keep getting the message Internal Server Error, and have to sign in again. What can I do?
Yours, Christer Karjalainen
christerkarjalainen@gmail.com

how large are the files you are uploading?

The maximum allowed file size is 500MB.

Try compressing the mp3 files into a zip archive, that may bring the file size down enough to allow the files to be uploaded.

The file is not even near 500MB, and it´s also zipped. Still does not work, which is pretty strange, since I´ve managed to upload files of approximately the same size before. And I have a few albums that I want to upload as mp3 albums for the shop. Now I have some of them only as physical CD albums...Of course the quality is better than mp3, but some people buy mp3 (people without musical ears...)

What browser are you using? have you tried using a different browser?

Please send a copy of one of the files you are trying to upload.