<i>I am leaning toward this being the OS related. </i><p> For what it's worth, I DID verify that setting the priority of the tester to match the dummy caller restores the normal execution time.
Also for what it's worth, I ran the same tests on Mac OS X. The same behavior results, except that the difference is more extreme (10 mSec --> 55 mSec). But matching priorities works there as well. <b>More information:</b> The dummy caller is not even necessary to prove the point - like Greg said, it is boosting the priority of the VI it calls, even though it doesn't execute. Without the dummy even loaded, if you set the priority of the time-waster VI to HIGHER than the tester, the penalty is imposed. <b>The rule as I understand it</b>: A time penalty is imposed when a VI calls a higher-priority VI. (Subroutine priority excepted).
