How do I troubleshoot "A non-SQL error occurred while requesting a connection from <DSN>." errors?

Hello,

Last week we began seeing some timeout errors, but today there have been much more of them and I’m not sure how to proceed in troubleshooting.

We have 2 load balanced app servers:

Windows Server 2008 R2 (virtualized)

ColdFusion 8, Enterprise

And a database server:

Windows Server 2008 R2

SQL 2012

The error in “coldfusion-out.log” is:

A non-SQL error occurred while requesting a connection from <DSN>.

Timed out trying to establish connection

This only happens on one of the web servers, but it happens more frequently when the app servers is under a heavier load. Most of the day it works fine, but 4 or 5 times throughout the day we will have 1 – 15 requests timeout in a row(always varies), and then things will be fine again w/out restarting or doing anything.

The database server is much more powerful than the app server, and I don't believe the issue involves long running queries or the DB server being under heavy load.

I’m a DBA who is temporarily handling System Admin responsibilities, and I’m not sure how to further trouble shoot this. I just started some pings going from the app server to the database using IP and the listeners name. How else can I prepare for the next time it happens. What other logs should I be looking at to gain some insight? Are there PerfMon counters I could use to help troubleshoot?

Thanks for your help!