apt GPG warning

[Alex Dean]

After running apt-get update, I got the following warning :

> W: GPG error: http://mirrors.usc.edu testing Release: The following  
> signatures couldn't be verified because the public key is not  
> available: NO_PUBKEY 010908312D230C5F
> W: GPG error: http://debian.mirrors.pair.com testing Release: The  
> following signatures couldn't be verified because the public key is  
> not available: NO_PUBKEY 010908312D230C5F
> W: You may want to run apt-get update to correct these problems

The suggested remedy is to run apt-get update, but that's what I just  
did.  Do I need to change to other servers in sources.list?

thanks,
alex

ps : This is my sources.list, if that's any help...

> deb http://mirrors.usc.edu/pub/linux/distributions/debian/ testing  
> main contrib non-free
> deb-src http://mirrors.usc.edu/pub/linux/distributions/debian/  
> testing main contrib non-free
>
> deb http://mirrors.usc.edu/pub/linux/distributions/debian/ stable  
> main contrib non-free
> deb-src http://mirrors.usc.edu/pub/linux/distributions/debian/  
> stable main contrib non-free
>
> deb http://debian.mirrors.pair.com/ testing main contrib non-free
> deb-src http://debian.mirrors.pair.com/ testing main contrib non-free
>
> deb http://debian.mirrors.pair.com/ stable main contrib non-free
> deb-src http://debian.mirrors.pair.com/ stable main contrib non-free
>
> deb http://security.debian.org/ stable/updates main
.