Random crashes when saving

I’m beginning to experience more and more crashes with WordPress when editing saved Posts and Pages.

I can trace the source of the crash down to specific word or line of code within the article, but as far as I can see, there’s nothing there that could cause a crash.

The crashes are totally unrelated and random (lists, links, em characters, a specific word et cetera) but entirely reproducible within the affected Page or Post.

I’ve copied all of the code out, cleansed it with BBEdit, all to no avail.

It’s incredibly annoying because it means the only way to circumvent this is to go straight into the database, which means the article is no longer editable via WordPress.

Anyone have the first clue what’s going on here, because all my years of PHP knowledge seem to count for bugger all right now…