I get the same exact error. I can usually hear the first few transmissions fine but eventually one of them will cause a the DRIVER_IRQL_NOT_LESS_OR_EQUAL error with the ha10kx2k.sys as the culprit. With my luck, it usually seems to happen when I'm transporting people in the helo.
I'm using an Audigy 2 ZS with the Atari version of the game.
In an earlier thread someone suggested disabling VoIP by adding "-disableVoN=1" to the command line but it doesn't seem to have any effect for me.