Pwerbook G4 1 ghz - 256 mb - osx - cubase sx - edirol ua 20

I am using Reason 2.5 under cubase sx - and having a really great time - everything working ok and some great sounds
starting to come out!

When I try to add some vocals by running the reason song
through cubase - using edirol ua 20 ( with updated osx driver)
i get terrible stuttering and drop out on the reason song
as it passes through cubase.

I i set the whole thing up again and just use a mic straight into the power book (alu) it all sounds ok

i have buggered around with buffer sizes etc - but i think i may be up against a bigger problem - - -

would an upgrade to sx 2.0 help - is it a really stupid and easy problem??

should i just bin the edirol and go firewire?

what does tha macmusic membership think???

the manuals do not seem to go into this problem at any length.......


here's hoping

gog