Slitherine

I am unable to download the main installer (1,7 Gigs). It says "download has been interrupted" and then it cannot be resumed.

I'd also like to mention the download speed around 200 kb/sec, which makes every attempt a 2 hour long slog. Two times already this happened!

Please let me know if there's any solution. I already own the base game, Morning Sun and Marines expansions but they are installed before the "World War II" overhaul.

You really made a mess with these changes...

Well everybody seemed to have been able to download the upgrade easily, so the issue must be in your side, or maybe your ISP.
Try downloading via another mirror:
http://ftp.eu.matrixgames.com/pub/Order ... e-v248.zip