Test output broken after upgrading to 2.3.1 from 2.0

Last week we upgraded from Go 2.0 to v2.3.1.  We had a set of pipelines building .Net applications that prior to this had run just fine with unit test results (using a procedure to convert the test output to a jUnit-compatible format that we found elsewhere in this forum).

Now, after the upgrade, the test output is no longer being correctly imported.  Can someone suggest what has changed to break our pipeline?  Or how I go about troubleshooting this?  The console output is singularly unhelpful and the documentation I can find is sparse at best.

Thanks in advance for any help....

Details

From the developer's email (from the stage console log):

Before upgrade I was using the below configuration, it was fine. 
 
[cruise] Uploading artifacts from D:\Cruise Agent\pipelines\Bid-Build\cruise-output\log.xml to cruise-output
[cruise] Uploading artifacts from D:\Cruise Agent\pipelines\Bid-Build\IM.Bid.UTC\testoutput\index.html to testoutput
[cruise] Job completed Bid-Build/Bid-Build-60816-62/validation/1/unittest on M-NET-BUILD [D:\Cruise Agent] at Fri Oct 28 05:19:52 EDT 2011
 
But, after upgrade the some configuration giving the below error
[cruise] Start to upload Bid-Build/Bid-Build-60988-68/validation/1/unittest on M-NET-BUILD [D:\Cruise Agent] at Mon Oct 31 13:55:09 EDT 2011
[cruise] Uploading artifacts from D:\Cruise Agent\pipelines\Bid-Build\IM.Bid.UTC\testoutput\index.html to testoutput
Ignoring file index.html - it is not a recognised test file.
[cruise] Uploading artifacts from C:\Users\jebastine_vetharaj\AppData\Local\Temp\cruise-2b727500-cb14-4710-a80f-972a2e986ef5\3efbc7d4-16d4-4e76-94d4-a7d17f82b76a\result\index.html to testoutput

There were no changes other than what the upgrade process might have done to the config.

The artifacts element is:

            <artifacts>
              <test src="IM.Bid.UTC\testoutput\index.html" dest="testoutput" />
            </artifacts>

(note: the above had the application name manually obfuscated so if there are any inconsistencies they may be mine)