Just double checking, in the Comparison Criteria table of what you're ignoring, the Enabled column is set to "Yes" by both of these rules? Your sure there are no spaces or anything after the "^:" that could be causing it to not find it?
In looking a little closer I do have another rule that could fit that, which means maybe I was having problems with that one also. Try a rule with this RegEx in it...
"^:Written by*"