MSTest Runner task fails if Bamboo is getting run as a SYSTEM user

If I run the bamboo application as "Administrator" the test runner (MSTest) runs as "Administrator" (and Runs).
If I run the bamboo application as "SYSTEM" the test runner (MSTest) runs as a different user instead of SYSTEM (and Fails).

build	17-Jul-2012 19:02:29	Loading JCPS/JCPS.Tests/bin/JCPS.Tests.dll...
build	17-Jul-2012 19:02:29	JCPS/JCPS.Tests/bin/JCPS.Tests.dll
build	17-Jul-2012 19:02:29	The directory name is invalid.