Well, issues only ever happen in multiplayer. Singleplayer plays fine. Issues also only happen in Civilization 5. All other games run fine.
I spent 8 hours on it yesterday and these are the errors I received:
*Entered some lobbies but could not click to go green (same as some others)
*Hosted some lobbies and some people could not click to go green
*Entered some lobbies and host could not see my text (but everyone else could)
*Tried joining some lobbies but got "multiplayer error"
*Played some games that froze for everyone on turn 1 (we could still talk but not move units)
*Played some games where it brought up the game load screen part-way through a game (e.g. turn 57 it brought up Washington or whoever I was playing as and "loading", then carried on playing normally another 10 turns till it crashed)
*Played some games that froze around turn 50-60 (we could still talk but not move units)
*Played some games that crashed around turn 50-60 (could not talk or scroll on the screen and after waiting 10 minutes with no change I closed Civ via Ctrl+Alt+Del). On the last one it happened when I tried to add a settler to the queue in my capital behind a catapult during the turn change - no idea if that caused it but that was what I was doing at the time. According to 2 Steam friends the game crashed for them as well, not just me.
Didn't manage a single full game in all that time, so perhaps you can understand the frustration! As for system specs it's probably easiest if I post my DxDiag? (attached)
There were no Steam (or other) popups at the time. I don't know if crash occurred during an autosave; the last crash was on turn 66 and my autosave is every 2 turns. I did not otherwise save or load the game (it was multiplayer) and had only been trying to play for 8 hours (that was more than enough) with errors in every game.
I had tried restarting Steam, restarting Civ 5, and rebooting, at various stages through the 8 hours. I was running the DX11 version of Civ 5, trying small and standard size maps, random leader.
I think I ran Steam validate (Right-click game, Properties, Local Files, Validate Game Cache). It found 1 bad file it wants to reacquire. However it doesn't reacquire the file, how do I make it do this? Thought about deleting the Civ game content and re-acquiring the lot from Steam but would at least like to keep the Hall of Fame first...