###EDIT solved###
Been messing around with the client now for a few houers,
i tried setting the sound to false in ic2, still breaking on startup,
problem is, i can see the error message for a bit, but it closes down before i can copy the content of it,
i tryed redownloading the ic2.jar mod again, same problem,
tryed the whole procedure a few times to spot errors, 
starting to wonder if i should just wait for the new version and tell my users on my server they should wait too,
###EDIT###
i'm sorry, i failed to isolate the error,
i ran IC2 without buildcraft, ran fine,
so i look at the site, saying its for minecraft 1.2.3,
doh, my own mistake all along, i hate building clients all the time, kind of wish we could do something about it to make it easy
"actually just dreamt about it", now i might be able to sleep again, sorry for the trouble
###EDIT###