Thanks for the reply Baron.
I have been using the default referral tracking - if I click on a link in my ad or signature on the merb site, it should register as a referral. Merb has always shown as the #1 entry in my referral traffic report, now it`s not even on the list some days, other times I see only a few entries. Interestingly enough I have seen entries from both https://merb.cc and merb.cc over the past week, I don`t know why it would still show as https://merb.cc? At the same time as I appear to have lost all my traffic from merb, suddenly my direct traffic to the site has increased by 1000%! I don`t know how GA knows that a hit is a referral, but something seems to be missing.
Thanks for the information about custom campaigns, this is most interesting. I will try this out and see what kind of results I get.