Connection Failing Randomly TCP Provider Error: 0

Here is what I got:

Sql 2005 std on windows 2003 server r2

tcp port 1433 set for connections in Sql 2005

Port open on firewall from DMZ 1433 can connect from web farm telneting from all IP address on port 1433 to sql both by name and IP.

the connection works 99.9% of the time.

No errors in the sql logs showing anything Firewall logs show no blocks. Windows firewall service is disabled to move that out of the troubleshooting.

connection string:

<add key="CommonConnectionString" value="server=servernameinstancename,1433;database=DBname;uid=username;pwd=mypass;Connection Lifetime=30" />



An error has occurred while establishing a connection to the server. When connecting to SQL Server 2005, this failure may be caused by the fact that under the default settings SQL Server does not allow remote connections. (provider: TCP Provider, error: 0 - A connection attempt failed because the connected party did not properly respond after a period of time, or established connection failed because connected host has failed to respond.)