why does yum want xulrunner?

[sean darcy]

from today:

yum update
............
--> Finished Dependency Resolution
Error: Unresolvable requirement libxpcom_core.so()(64bit) for yelp
Error: Unresolvable requirement gecko-libs = 1.8.1.6 for yelp
Error: Unresolvable requirement libgtkembedmoz.so()(64bit) for yelp
Error: Missing Dependency: firefox is needed by package libswt3-gtk2
Error: Unresolvable requirement gecko-libs = 1.8.1.6 for devhelp
Error: Unresolvable requirement libgtkembedmoz.so()(64bit) for devhelp
Error: Unresolvable requirement libgtkembedmoz.so for devhelp

yum --exclude=xulrunner update works.

and xulrunner is not installed:

rpm -q xulrunner
package xulrunner is not installed

sean