So I'm in a game, and I cannot progress to the next turn because a decision is expected from me, according to the game. Two other empires are giving me this notification, and I cannot progress. I have no idea what the decision is, or where I'm supposed to make it. I've only been playing for half an hour or so so I'm probably going to look pretty dumb for this, but what am I supposed to do? 

Click on the hands icon covering the End Turn button and it should take you to the screen where you need to make a decision about a diplomatic proposal.  If there's nothing there for you to agree to or refuse or counter, then I suggest you submit your current save as a bug report.  Earlier builds had a bug like this when you received multiple proposals from different AIs on the same turn, but it seemed to be fixed prior to the Victor OpenDev.  I haven't encountered it with this build, but your situation looks like a variant of the same bug, so I'm sure the dev team will want to look at.

Thanks for your response. I will submit it as a bug report. I just wanted to check here first to make sure I wasn't missing something obvious.