This bug has been copied from bug #688926 and has been proposed to be backported to 5.6 z-stream (EUS).
in kernel-2.6.18-238.10.1.el5 linux-2.6-usb-fix-usbfs-isochronous-data-transfer-regression.patch
An advisory has been issued which should help the problem described in this bug report. This report is therefore being closed with a resolution of ERRATA. For more information on therefore solution and/or where to find the updated files, please follow the link below. You may reopen this bug report if the solution does not work for you. http://rhn.redhat.com/errata/RHSA-2011-0833.html
Technical note added. If any revisions are required, please edit the "Technical Notes" field accordingly. All revisions will be proofread by the Engineering Content Services team. New Contents: This update fixes a bug in the way isochronous input data was returned to user space for usbfs (USB File System) transfers, resolving various audio issues.