I too am having trouble. I have a category for a blog setup called school of music. I would like only this category to have a perticular widget appear. I have also set up a tag called school of music and have tag all the blog posts.
I cannot get the widget to show up on each blog using the categories or the tag.
FYI, I have selected show on selected. I have nothing checked. I have entered the following target URLs:
school-of-music (this worked to show up on the page that lists all the blog posts)
category/school of music
tag/school of music
tag/school of music/*
2011/11/* - this worked, but I'm think if I post another blog outside of this category it will show up on those pages too...correct?
Thanks for the help!