Here's a workaround that works:The installation process can be continued just by killing the apt-cdrom process (Alt-F2, Enter, ps, find out the PID, kill the process).
And for those crying that 'YOU CAN'T INSTALL JESSIE! THERE IS NO WAY..!' No matter how loud you are, you just are not right. For your urgent needs (all needs before jessie releases) just install wheezy and update it afterwards.