What exactly are you trying to do/upload? If you look at the ref sheet in my profile, you'll notice that the OOH MAGIC was created as a photoshop layer with transparency. When I uploaded the image, I created a smaller one because the original was too high resolution, and then I converted it (which rasterized it) into a .png. If you're using gimp project files or Paint.Net, don't upload the project files. Keep the original and upload it as an image format that doesn't have an alpha channel. If you need to send an image with layers/alpha channels, use email.
Unless of course you're talking about social transparency. In that case, just be yourself and others will follow in time.~

save it as an interlaced png

Ahh! This was the issue! Thanks!