I bought the game ages ago on DVD, absolutely loved it as far as I could play it, but got to a point where the game crashed consistently when trying to load one of the levels ("Over the Rainbow").

The game had a patch available, but it didn't help, and so I put the game aside. Until today, when I noticed it in current GOG sale, and decided to try again. Unsurprisingly the game was still crashing at that point, but after a bit of reading I thankfully I saw someone's comment about windowed video mode not helping their problem, and it occurred to me that I hadn't tried using that for MY problem; and sure enough it worked!

In a windowed video mode, the game happily loaded the level. I tried switching back to full-screen right away and that was still fine, so I kept playing and completed the level. I then quit and reloaded the game and tried reloading "Over the Rainbow" again (still in full-screen mode), and that was fine as well.

So it was seemingly something to do with loading that level for the first time.

In short, if the game is crashing, try a windowed mode.

p.s. I also read about the save-game corruption bug, which I'd not heard about previously. Clearly it's a good idea to take regular backups of your save file, lest you get bitten by that and lose all of your progress!