So, I was playing this over multiplayer using Hamachi and everything was working great. We decided to save the game for later, but when the host tried to load the saved game, the connected client players lost their connection. I tried this several times and I was unable to reload our save game over multiplayer.

Is reloading a multiplayer game not possible, or is this just a bug? Either way, it's unacceptable. How can you expect to play through a 4X game like this with your friends in a single session when games can last days? This is the main reason why I bought this game, because there are very few 4X space games out there with a real time multiplayer feature. This essentially makes multiplayer unusable.

Can someone confirm this problem and can it be fixed?

I have run into this problem 1 or 2 times, I suggest you keep 2 saves.
It is a bug, what i think that happens is the saves are either not synced or there was a corruption during the save process.

I generally keep 3 saves and cycle thru 2 at a time so i have 2 new ones and one older one. Its a pain but its better than losing 9hrs on a PAX game