Hi Dave,
I remember that there was some discussion about this subject some time ago. As far as i know Xara does support multicore configs. I´m running it on a quad core (Intel Core i7, 4+4 core units) and it does take advantage of at least four cores (the other four are virtual units - Hyper threading technology by Intel). I assume that it does the same for AMD processors. I don´t remember anyone reporting problems with AMD processors before. I´m sure someone will step in and will give some more help.