[ic] Changing the Last Order Number

[Cameron]

Ok, I changed this in another site that's currently live, on IT TOO things
were perfectly ok until i changed the Last Order Number. Now the
auto-creation of users (in log_transaction) fails. This is three times on
three seperate sites that this has happened to me, this is WAY more than a
coincidence, surely someone else has some across this? has noone else EVER
changed the order number? i'm completely baffled here, that something that
appears somewhat inert is breaking something seemingly unrelated. Anyone?
Any ideas? What on earth could this be?