much more likely to be a DNS issue i would think; since it appears to happen once in a while, and not 100% of the time, I'd venture the guess that the connection string pointsd to SERVERNAMe or SERVERNAME.DOMAIN.COM, and once in a while that can't be found.
connecting by IP address is an option, but I'd throw this at the network guys and have them check that all the DNS entries are correct.
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