dnsserver problem

Hello:

I installed squid 1.1.20 and sometimes I get the following error
message:

ERROR
The requested URL could not be retrieved
While trying to retrieve the URL: http://www.excite.com/
The following error was encountered:
     DNS name lookup failure
The system returned:
    DNS Domain 'www.excite.com' is invalid: Host not found
(authoritative).

DNS is working, nslookup www.excite.com answers:

Name: ldwww1.excite.com
Address: 198.3.98.99
Aliases: www.excite.com

This happens randomly with different addresses.

Why is that and how can I fix this problem?

Thanks a lot

-- 
Ernesto Ordonez	
e-mail: ernesto@mexico.sgi.com
Phone (525)267 13 67