em0 problems on t41 after updating to 5.3

[nbco]

Hi list,
I have the following problems after updating from 5.1.2.1 to 5.3-BETA7

I have extemely poor and intermittent network connectivity with my 
ethernet card (em0).  My wireless atheros card (ath0) works perfectly. 

I have kde installed.

With em0:
I can ping; I can't telnet; sometimes I can send and receive mail (I 
mean very intermittently I can send a test message in about 12-24 
hours).  In terms of net access, I can access the web but extremely 
slowly with frequent timeouts, freebsd utilities are subject to the 
same issues, such as portupgrade; links; and cvsup, so I don't tend to 
think this is a kde problem.

I have no DHCP entries in my rc.conf.  Interestingly with both em0 and 
eth0, when  executing dhclient I receive the following error message:
dhclient: send_packet: Network is unreachable.  
However, with ath0 this is clearly a lie, as the network works 
perfectly. 


I have tested the ethernet card (em0) in my dual boot windows install, 
it works fine, so it doesn't seem to be a hardware problem.  My other 
box on the network is also fine.

Any ideas would be most gratefully received, I'm totally clueless on 
this.
many thanks
.nbco