Question : External web site and same name domain broke

I have a trusted domain with the same name as our external web site. I have an A record in DNS in both domains to point to our external web site. I have had no problems until this morning. I cannot ping our web site, or get to it in any way using both URL and IP address.
Here are the results of NSLOOKUP:

U:\>nslookup www.securityfinancialbank.com
Server:  dc-durand.securitynationalbank.org
Address:  10.1.1.99

Non-authoritative answer:
Name:    www.securityfinancialbank.com
Address:  64.33.128.150


U:\>ping www.securityfinancialbank.com

Pinging www.securityfinancialbank.com [64.33.128.150] with

Request timed out.
Request timed out.
Request timed out.
Request timed out.

Ping statistics for 64.33.128.150:
    Packets: Sent = 4, Received = 0, Lost = 4 (100% loss),

The web site is ok from outside our network. Any ideas on what happened and how to fix it?
Thanks!!!

Answer : External web site and same name domain broke

Do you have Host a record in dns for securityfinancialbank host name.
If yes
Then clear cache in the system by Ipaddress /flushdns

then try to ping the same

Because all the request will search in DNS first and then only they go for private ip...!