Here are a couple of ideas...
(1) Put a Delay 100 or Delay 1000 before the active part of the script, and follow it up with a ResetTimer to resent the clock to zero.
The extra 0.1 to 1.0 sec's gives the browser time to "settle" and this should elminate any artifacts due to the OS.
(2) Maybe try using the SaveRecord command to output timing data.
* Here are the detailed instructions for use of the SaveRecord command, which outputs in-progress test data to an external file: http://www.e-Valid.com/Products/Documentation.9/Playback/saverecord.html
(3) The interval you choose to retry in active synchronization commands affects the precision of the timing. The fastest you can go is 100 Hz, meaning 0.01 second resolution, but that rate is right at the edge of the point where the synchronization overhead becomes a significant (> 1%) of the CPU capacity. We like to use 10 Hz, or 10 per second, so that the timings are correct within 0.1 seconds +/-.
eValid Suppor Team