interesting. I am under the impression that a multi just makes calls to the singles. So if you create a multi with 4 different single sounds and then dump that multi to a sequencer, basically it is only dumping the data that says which singles are used and what parameter tweaks you did to the multi, right? so if later on, I go and mess around with one of those singles and store it over the current single, when I dump the original multi back into the virus, it will still make a call to that single (that I had just tweaked), but now the multi will sound different as the single that it makes a call to has been changed. am I thinking about this correctly?

That will only happen if you dont save the multi single then you do a program change to a new sound for same part. When you change back the part will call up the address of the sound its refering to so if you have tweaked it then thats what you will hear. But if youve saved it in a different slot to the original it will recall that address instead but you will still hear changes if youve tweaked that one. My understanding is that this will only happen if you do a program change. Just like when your in single mode and you change to new single after editing, when you change back you will hear original sound again unless you saved first. This can quite easily happen when more than one part is using the same sound but then again if your only using 16 sounds or less with no program changes it wont happen. Therefore if you dump an arrangement with 16 parts being used perhaps with same sound more than once then everything will be restored as is when you reload.Its taken me a while to get my head around this but I think the virus is finally beginning to take over my brain. :lol:
Anyways I resolved my problem re sysex midi dump. Thanks to all those who offered there genuine help, Im really embarrased :oops: it was such a simple thing, I had the midi rx disabled, its all working fine now that Ive got a peptic ulcer and migraines :) .