The client only expects to receive DNS replies from UDP port 53. As you are getting a respone the port number shouldn't be a problem.
You can try this command on the DNS server (for your eth0 NIC) to see the DNS traffic.
The delay may be because you have multiple DNS servers defined in your client's resolv.conf file, and one of the servers isn't responding. You can use this command to test DNS queries against a specific host, and see whether it has the right answers. It will help eliminate bad DNS servers and you don't have to be the root user to do it.
tcpdump -n -i eth0 port 53
# host wedsite-name dns-server-ip-address