>Does anyone of you know this error?
I guess I do.
I bet you are on Ubuntu... Try this:
sudo apt-get install build-essential ruby1.8-dev
I am pretty sure you are missing at least one of these packages (According to the error, it seems ruby1.8-dev).
If this still does not help (but I am almost sure it will), just ping me, we will try to find out something.
Have a nice day,