Maybe you've got some parental controls that are blocking access from Scratch to the internet? If so, you could try setting them to allow Scratch...
Or, your internet connection may be too slow... I forget how to fix the connection, but you can make your project smaller by going to the Edi menu, and compressing some sounds or images.
On the other hand, your project might be to small for upload... Try un-ticking the box on the upload form that says "compress sounds and images".
Hope this helps
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