So, a friend and I just tried to play Original Sin together, but the game seems intent on not letting us do it in peace.
In character creation, his UI was all sorts of messy, not letting him pick skills and showing some graphical errors (his shield was floating beside him http://i.imgur.com/xw1J4i7.png ).
Once we got past that little hurdle by having me create the characters as we had agreed, once inside the game he was unable to see any interact-able objects (shells on the beach or the corpse near the start of the game). Also his shield was still floating beside him on his screen.
I should point out none of this happens in single player. Could it be a connection issue somehow? We are very far apart.

Pictures below.

http://i.imgur.com/jgX1keA.png Alone

http://i.imgur.com/yDW7R5f.png With friend

We are using some graphical mods, but as I said the bugs didn't happen in single player. My friend is also unable to post on this forum (the button shows "please wait processing" for a while then goes back to "post my message") either through Galaxy or his browser, but that probably doesn't have anything to do with the issues in-game.

Sorry about the delay in replying, I've been very busy so we haven't had a lot of chances to try playing together. We both removed all mods and verified our game files, and verification did make some changes for me. However, when my friend tries to host and I try to join, I get a crash while it's on "Loading Character Generation". We're going to try the other way around again now, but I wanted to link you to a crash dump: MediaFire link.

Edit: Same problems as before when I try to host. Is there any logging we could enable that would be of use to you? I'm hoping the crash log tells you something (I consistently get that crash when he hosts).

Okay so I was the OP/friend before gog decided to not let me post. We've tried the original arrangement with me not hosting and the issues persist; I see graphics where they don't belong (shield floating to the side no interactable objects) and the game won't even let me use skills.

We've been trying Direct Connection, I don't think invites worked for us (possibly related, who knows). I guess we can try the lobby as well. We both have the latest version of the game ("2.0.119.430 (LANG HOTFIX)"), set to auto-update, and my friend has already tried reinstalling the game once (we've both verified the files as well).

We both tried verifying the game files again, but it didn't change anything. Invites definitely don't work. We receive them, but accepting them does nothing. We tried using the lobby instead and it made no difference with me hosting. With him hosting, joining through the lobby instead of a direct connection got me to the character creation screen, but both characters had 4 skills, and a few seconds later it crashed again (crash dump).

Edit: We tried turning off everything anti-virus or firewall related but it made no difference either.

How would we go about that? Simply bypass Galaxy and download the game directly from the website?

We rolled back to the pre-Galaxy 2.0.119.430 update through the Galaxy client, but the problems remain (I still crash trying to join him, and he still gets the buggy behavior joining me). We haven't tried playing with other people yet.

Edit: We also tried letting him make the characters. Once he's in-game I *can* join without crashing, but I have the same problems - I can't use skills, and there are no interactable objects.

I'm online at pretty much all hours and I'm closer timezone-wise.

Same, I've been raiding all evening so I'll drop an email or something :p

Problems turned out to be on my end, and a full reinstall fixed them. Thanks!