[CentOS] Module signed with unknown public key

I recently had a hard disk failure on my CentOS-6.4 server.
I re-intalled CentOS on a second disk, and this is working fine.

But I put together the old system -
most partitions on the old disk could still be read -
and made a working system.
But when I re-start this system
I get the above message many times.

(Also I can only login in text mode,
and when I run startx I get the error
"Fatal server error: no screens found."
And ifconfig only gives the lo interface;
it does not show eth0 and eth1,
so I am unable to access the internet.)

But how can one "sign" a module?
I googled for this, but all the suggestions
were about signing modules while compiling them.

It seems odd too that the error message does not tell me
which module it is referring to.
But the error is repeated about as many times
as the number of modules listed by lsmod,
so I guess every module is wrongly signed.

Any enlightenment on this subject gratefully received.


-- 
Timothy Murphy  
e-mail: gayleard /at/ eircom.net
School of Mathematics, Trinity College, Dublin 2, Ireland