Hello Jeff, > I spent some months hunting for possible causes in my driver code > (and I think I may have raised the issue here) but got nowhere The same thing. I encountered it several years ago in XP, 2003, Vista and Win7. Asked here and in MS newsgroups but no success. Finally I have added my own IOCTL_KS_READ_STREAM/IOCTL_KS_WRITE_STREAM processing. Regards, Eugene ****************** WDMAUDIODEV addresses: Post message: mailto:wdmaudiodev@xxxxxxxxxxxxx Subscribe: mailto:wdmaudiodev-request@xxxxxxxxxxxxx?subject=subscribe Unsubscribe: mailto:wdmaudiodev-request@xxxxxxxxxxxxx?subject=unsubscribe Moderator: mailto:wdmaudiodev-moderators@xxxxxxxxxxxxx URL to WDMAUDIODEV page: http://www.wdmaudiodev.com/