Out of date mirror for whom? I currently have the same gnokii as you do (6.2.27), but yum is complaining that it now wants to update it to 6.2.29 but can't as kdepim (and others) have a dependency on the old version. Unless I've misread the error message?
gnokii-0.6.27-2.el5.x86_64 is the package listed in your yum output but the dependency trying to be satisfied is libgnokii.so.4()(64bit)
On my system I can see that dep in EPEL given by the package I mentioned.
Looks like an *EPEL* mirror issue or something being cached badly between you and them...
This is not a *CentOS* repo though....
James