If a user fails to access a given session for longer than the screen lock idle timeout interval while an application is accessing a USB device -- for instance, while copying a large number of files to or from a USB flash drive -- the session will be locked. With RHA, NSCM, and authenticated smart cards, this means the session detaches and all USB devices disconnect from the session. This can interrupt or abort the application's access to the device.
The following workarounds are available:
Advise users to monitor their USB device usage to avoid being timed out
Set the timeout interval value high enough to allow I/O to complete before the interval elapses
Disable the screen saver
Disable RHA
The last two alternatives are less desirable because they each remove a level of security.