Lene wrote:
...don't read too much into it: they're still hanging out with you, so they obviously enjoy your company.
That's true.
It's coming back to me. I have known some nice people, in the distant past. It's just that I've been stuck in this prison so long, it's like I've forgotten what the sun looks like (not literally).
Sometimes a cool-down means something important, sometimes it doesn't. You should make some effort to figure it out (you don't sound like a total clod) but at the same time, don't make yourself crazy when there's nothing to gain.
TheIndignant -- You didn't mention how old you and your friend are. Four years can be a long time, with lots of changes. The friendship could cool off for a while, then become important again later in life.