> Thanks Sl�vek. Thought I would give this a try . It did resolve
> mirror.xcer.cz but the connection then timed out over 5 tries. Perhaps
> someone else might try this in case for some reason my IP address is a
> factor ? Ping mirror.xcer.cz also failed.

$  ping mirror.xcer.cz
PING mirror.xcer.cz (91.241.23.210) 56(84) bytes of data.
From 10.2.252.114 icmp_seq=2 Destination Host Unreachable

Here from Berlin, Germany. However, "10.2.252.114" looks suspicious to me, 
because netrange  10.0.0.0 - 10.255.255.255 is a private address usually used 
by internal networks of big company IIUC, i.e. my provider. When I ping the 
Freie Universit�t Berlin, I get this:

$ ping 130.133.4.195
PING 130.133.4.195 (130.133.4.195) 56(84) bytes of data.
64 bytes from 130.133.4.195: icmp_req=1 ttl=52 time=24.6 ms

I don't know if anything of this is relevant to your problem. At least I can 
confirm, that I'm not able to ping mirror.xcer.cz.

Hope this helps.

Regards, Stefan