Steam wants me to reinstall Civ5(Vanilla)

[Heerlo]

I'm having a problem with Steam/Civ5.

Me and my brother were about to continue our Civ5 multiplayer game on LAN with the same copy of Civilization 5.We have been able to do this for a long time with the same copy.But today we started trying to do it, and Steam now wants me to reinstall Civ5.

Anyone know what would cause this and how to fix it?I don't have to know.I'm pretty sure I can just reinstall it from the disk.

But if I decided to reinstall it and remove my save files not to lose them, I'll be able to put them in and reload them right?Mostly because I have a story over in S&LP that I want to keep going.

Thanks in advance.

Edit:Got it reinstalled, and it works fine now.But does anyone have any idea what would have caused this to begin with?

 

[timtofly]

Using the same copy of Civ5 on two different computers at the same time is illegal.

 

[Heerlo]

Using the same copy of Civ5 on two different computers at the same time is illegal.

Really?