Mongod crashes with access denied if you spawn multiple shells inserting in quick succession

Created a simple script that drops a database and inserts a 1K document in a tight loop. I launch 20 of those in quick succession and this causes the database to crash. I can repro with 2.1.1 and the latest 5/28 build but not with 2.0.5.
Attached log file from the crash. To run the test, run load.bat from the zip dir.