Thanks for the replies. Some details: Connecting to Exchange 2007, not sure what OC backend - but I think I heard 2007, yeah using Outlook 2011 as well (no problems there - integration seems ok), nobody around me really uses a Mac... all Win 7 users... I did try un-installing it, but then afterwards realized all the preference files still existed, so I've now nuked those and reset everything... seems to be ok now, but will leave it for a few days to see, have all the patches possible for OC and OSX. Glad to hear it's working for others. I thought initially it was hardware as well - but when I don't run OC my MBA flies... no issues.