Noders are generally confident in their knowledge of the English language - even down to the minutiae - but in deference to non-conformists everywhere, this noder shall admit to ignorance.
It has happened before. It will happen again.
Churning through an old Ursula K. Le Guin novel, I am assaulted again and again by a minor irritation, until my conscious mind spots it: "Dreamed! Isn't it supposed to be dreamt!?" As it turns out, both are actually correct and thus I was impelled to find out why.
Dreamed and dreamt are different in their representation of the past-tense form of dream much for the same reason that flavor is spelled differently than flavour. Newton's 3.14 Law of Physics states that there must be tiny differences in languages spoken on different land-masses simply to make grammar and spelling bees that much more difficult. A'ight, alright - it is simply a difference between American and British English.
Dreamed is the American past-simple form of dream, while dreamt is the British, sometimes referred to as the "irregular" or T-form. Please note that British is used as a descriptive to also mean the more traditional English. T-forms seem to be on the decline in both American and British English. Consider some more examples:
Burn burnt burned
Lean leant leaned
Learn learnt learned
Smell smelt smelled
Spell spelt spelled
Spill spilt spilled
Spoil spoilt spoiled
Notice that these are T-forms in which the vowel being sounded does not change. There are also some T-forms in which the vowel sound does change that are still quite common (crept, dealt, dreamt, felt, leapt, meant). The fact that dreamt is in that list explains why, even as an American, I might still favor (favour?) using dreamt instead of dreamed.
Sweet dreamts! D'oh!! Even as an ESL teacher, I'll never get this language.
locke baron says: There's also the quirk that some T-forms hang on as adjectives (I burned the toast, now I have a bunch of burnt toast...)