In the process of committing updated code for WP 2.8 to wordpress subversion repository. Due to changes in rendering multiple widgets, version 6.0 of Sideblog breaks backward compatibility. Additional work can be done to make it so but in the meantime to address the needs of those who have already upgraded their wordpress to 2.8, this version will suffice.
To upgrade, I suggest deactivating the plugin and go through the usual installation process. I have not thoroughly tested (as usual) the code, so any bugs please leave a comment.