I had the same problem with TP2. I tried the installer several times. I did get it to work, but the problem I found was that one of the packages was causing a conflict (intall everything option), and then answering the dialogue terminated the pkg install. I tried again w/o that package selected and it installed all the CDs. I cannot remember the package, but if this is your problem, it should be what causes synaptic to want to exit, I think it was specified in the dialogue.
I was going to try installing the beta later this week. I will repost if I dont see any better possibilities here.