d'oh.
i don't use key signatures. i just use bars to reset. that means i need to be extra careful when i'm splitting up tracks into bass and treble parts, and i wasn't. that means i'm going to have to fix a few things and reupload the mixes....
i just find that key signatures don't really matter. i mean, i don't use them when i'm writing. most of the time something is there, i just can't be bothered to work it out.
what i had, for example, was a written out Gb on the bass note that told the computer that the G in the melody for the bar is flat, but i ended up getting G natural on the render because when i took the bass out the computer lost the instruction.
it may clarify a few things, but the notes are so fast it's hard to tell...
i'm glad i caught it though. it won't take long to fix.