I'm pretty certain it's a security feature of our web host and, as I said, we don't have control of it at this point unfortunately. The only other thing I can suggest, besides the specific programs I mentioned (XnView is free, so if you haven't tried it, you could experiment with the Export function), would be to try saving into a different format, e.g. PNG. It's definitely *not* a size issue.
- Oshyan