Getting comments from two categories - separated

Hi, I am a new member. On my multisite I want to fetch and show the latest comments from my blog owners (sub-directory) on the main blog, separated on category slugs. My blog owners are forced to post in one of two categories. I want comments from posts in category A to be shown in the left sidebar, and comments from posts in category B to be showed in right sidebar. My present solution doesn't work well. ( http://www.litteraturbloggen.no )
I am perfectly satisfied if I have to add some code into my sidebars. So: are any of your plugins/widgets capable of doing this? If so, I am the happiest man on the planet, at least for a while.