So, when i start up hammer, load my map, i select the "select" tool. Instead of selecting stuff, it switches to "z" mode. (press z and you will know what i'm talking about). Even on the top view its like this, it just moves the screen instead of selecting anything. What's happening?

I have same problem very often. But the victory is mine when I press the z-key and mouses 1st like a crazy...

I think the key for this is Ctrl + Spacebar or something like that.