Our ccnet was displaying a number of /warnaserror messages in our build notifications, even though the solution had no build errors or warnings.  We started digging through the files, and realized that this was because our project was set to "enable build warnings" in the build section of the configuration manager, which was supplying /buildaserror to the commandline.  This would get picked up by the ccnet xsl since it was looking for 'warning' or 'error'. 

To fix this, we changed the compile.xsl to look for ' warning' and ' error'.  The initial space stopped catching the /warnaserror arguments, but still catches real warnings and errors. 

Related question, who's using the <solution task vs. the <csc / <vbc tasks in nant?