Update: Fix is live in update 1.0.9. Thank you all who helped sort out the issue!
Dear all,
A critical bug has been found and reproduced successfully by me on Mac OS X. Anyone who hits an area where there is an achievement is affected by the bug. The game "freezes" and you cannot progress any further. Neither 'Load Checkpoint', nor 'New Game'/'Resume Game' will fix it.
I apologize for the inconvenience! Working on a fix and I hope to upload one by the end of today.