The software is not from a trusted source ???

[Alan Cox]

> I was just rather surprised to see this message and would like to know
> if packagekit is getting "more sophisticated" or there was some slight
> problem with one of the packages (unsigned?) 

Or the copy on your mirror has been tampered with so has a bogus
signature. It's not something you should treat likely. Sure 99.9% of the
time its probably a process error in producing the package or if you've
added extra repositories and it comes from one of them you may not have
imported the needed key.

But it might not be, and one day someone will trojan a mirror site and
people who disable and ignore the signing checks will get burned.

Another thing to check btw is that the package is simply not corrupt in
the download. Yum used to be very stupid about this and would keep the
corrupt package cached and keep erroring it. I've no idea if it was
fixed - but see if yum clean all then updating fixes it.

Alan