Can't update to Minecraft 1.4.6

This happened a few days after I updated to Minecraft 1.4.6.

I started up Minecraft

*What I expected to happen was:
Minecraft 1.4.6 would start as normal.

*What actually happened was:
The version was Minecraft 1.4.5??? I had updated so I don't know why I was on 1.4.5. I tried starting up Minecraft again and it was still Minecraft 1.4.5 and I wasn't asked if I wanted to update either.

Steps to reproduce:
I don't know because I don't know why it happened.

This hasn't happened to any of my friends.