Hmmm, you're right, it won't accept 2 tech requirements. This is interesting, as I'm sure it used to work fine in the Version that shipped (or was it the .99 demo?).
Just wanted to add it did indeed fix that problem, though now I have to figure out another good way of limiting you from having some of the 'better' shield types to early on... & of course I need to figure out a way for the computer to even realize it should build them as well... but that can wait a bit...