The problem is present in the RHEL3 U4 beta kernel. The fix is available and signed-off upstream: http://linux.bkbits.net:8080/linux-2.5/diffs/drivers/net/tg3.c@1.218?nav=index.html|src/|src/drivers|src/drivers/net|hist/drivers/net/tg3.c
*** This bug has been marked as a duplicate of 138738 ***
A fix for this problem has just been committed to the RHEL3 U5 patch pool this evening (in kernel version 2.4.21-26.2.EL).
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 the 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-2005-294.html