It seems another issue has turned up, though this one is pretty minor and easy to work around (until we get it fixed):

In every chapter, there is a "Master Puzzle", which is unlocked in one of the three rooms, but cannot be completed until the very end of the chapter. When you unlock this Master Puzzle, the Puzzle button flashes, but when you click the button, you just get a message saying that you'll have to wait till the end of the chapter to play the puzzle.

In the first 4-5 chapters, every room has a puzzle in it and all puzzles except the Master Puzzles can be played immediately.

The way to avoid the bug is to wait until you've found all the objects in each room before you click the puzzle button, which is what most players seem to be doing anyway (which is probably why we haven't known about the bug .)

If the last room you search is the one with the Master Puzzle in it, you won't have to click the Puzzle button - you'll be taken automatically to the Puzzle after the final flashback in that room is played.

Another (very minor) glitch I've found, at least in the Easy mode, was if you found all the required keywords to pass, and have a puzzle remaining, you can still pick more objects related to the last keyword you had selected. It plays the flashback each time you do so. It's nothing major, and it's not like anyone would /really/ keep picking objects after they'd found the last one. It's just a little something I noticed. ^^'

That's not a bug...it's a FEATURE!