Could you be a little more clear on this? Are they not working when sending trackback links to your past blog posts? Are they not working when sending from your WordPress.com blog to another blog? Or are they incoming trackback links to your blog?
How long have you waited between posting and looking for the trackback?
Mine are working fine for intrasite links and external links, as well as incoming. I just checked.
When I link to a site’s post in my post~the trackback doesn’t show up at the site I have linked to. Others that have linked to said particular site’s post do show up. Do all themes support this or just some?