sql server port security

we have two instances of sql server 2005. Recently we have blocked the ports over the network and kept 1433 open for the sql server. but sometimes it is observed that SQL server is not connecting. What could be the reason for this? Specially incase when we are trying to connect through crystal reports.
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Chris MConsulting - Technology ServicesCommented:
Sometimes SQL server 2005 is setup with dynamic port configuration, meaning that port 1433 might not be assigned to the service when it's restarted.

Investigate which port SQL server is running on when your applications fail to connect.

Secondly, there could be something that blocks you from connecting to port 1433. So do a virus scan on your client machines.

I have seen some people who fail to connect to SQL after virus attacks before.
The options are many but the best time to diagnose this is when the issue arises again.

Also check your logs (history) to see if there are any messages which coudl help you trouble shoot this faster. Just bear in mind that the causes can be many.

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Microsoft SQL Server 2005

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