No Accept-Ranges in script?

Hi,
I’ve tried to use Paid Downloads at my site to sell “photo archives”
One file is usually 300-400 Mb in ZIP format.
So, Paid Downloads works perfect with Paypal, then sends encrypted download link.

BUT !

The php-script DOES NOT SUPPORT “Ranges” (or Range: bytes) for the download.

So, it terminates the download and does not support partial download…
I’m not a programmer, but in simple words I want to explain:
Every time I try to download 300Mb zip-file – it goes well till 10-15% and then suddenly ends saying “download complete”.
While, of course, the download wasn’t complete.
I cant resume download – as the PD-script does not understand “resuming” and “downloading from certain byte, not from beginning”

I am sure this is common technical issue – so I would be grateful for your advice on how to solve it.

Can anyone help?

http://wordpress.org/extend/plugins/paid-downloads/