Patch 3.1 – we’ve been waiting for it.

I had a similar issue, but it was quite a while ago, so I can't say for sure what helped back then. I installed patch 1.6 on version 1.5, the installation went smoothly, but the game still showed version 1.5. Then I did the following: I completely uninstalled and reinstalled the game, and after that, I installed all the patches in order – that's what helped me back then.