Do you mean like this? http://www.hardwarecanucks.com/forum/water-cooling/65754-broken-screw-post-waterblock.html
You can remove like this if thread is still inside - https://www.youtube.com/watch?v=pbRRewJzbKI
Aquacomputer will send you new ones. Mine took about a week to come.
Ya, exactly like that, but one of the ones around the core. Thanks for the info!
I sent an email yesterday, but haven't got a response yet. Will see what they say.