NETDEV WATCHDOG: hsi0: transmit timed out

Issue

After updating from RHEL 5.3 to 5.8 (via "yum update" command, downloading packages from Redhat site) we have a problem using VNC graphical interface (both gnome and twm): when the graphical window appears, just after few seconds the network interface hangs (without error messages); after a couple of minutes, the network interface does a successfully recovery, but working again with graphical interface leads to the same error.
Under RHEL 5.3 all works fine (problem occurs just after the first reboot following the update).

After several errors, dmesg command shows:

   NETDEV WATCHDOG: hsi0: transmit timed out
   qeth: Recovery of device 0.0.70fc started ...
   qeth: Device 0.0.70fc/0.0.70fd/0.0.70fe is a HiperSockets card (level: HSEC)with link type HiperSockets.
   qeth: Hardware IP fragmentation not supported on hsi0
   qeth: VLAN enabled
   qeth: Multicast enabled
   qeth: IPV6 enabled
   qeth: Broadcast enabled
   qeth: Using SW checksumming on hsi0.
   qeth: Outbound TSO not supported on hsi0
   qeth: Device 0.0.70fc successfully recovered!
   NETDEV WATCHDOG: hsi0: transmit timed out
   qeth: Recovery of device 0.0.70fc started ...
   qeth: Device 0.0.70fc/0.0.70fd/0.0.70fe is a HiperSockets card (level: HSEC) with link type HiperSockets.
   qeth: Hardware IP fragmentation not supported on hsi0
   qeth: VLAN enabled
   qeth: Multicast enabled
   qeth: IPV6 enabled
   qeth: Broadcast enabled
   qeth: Using SW checksumming on hsi0.
   qeth: Outbound TSO not supported on hsi0
   qeth: Device 0.0.70fc successfully recovered!
   NETDEV WATCHDOG: hsi0: transmit timed out
   qeth: Recovery of device 0.0.70fc started ...
   qeth: Device 0.0.70fc/0.0.70fd/0.0.70fe is a HiperSockets card (level: HSEC) with link type HiperSockets.
   qeth: Hardware IP fragmentation not supported on hsi0
   qeth: VLAN enabled
   qeth: Multicast enabled
   qeth: IPV6 enabled
   qeth: Broadcast enabled
   qeth: Using SW checksumming on hsi0.
   qeth: Outbound TSO not supported on hsi0
   qeth: Device 0.0.70fc successfully recovered!
   NETDEV WATCHDOG: hsi0: transmit timed out
   qeth: Recovery of device 0.0.70fc started ...
   qeth: Device 0.0.70fc/0.0.70fd/0.0.70fe is a HiperSockets card (level: HSEC) with link type HiperSockets.
   qeth: Hardware IP fragmentation not supported on hsi0
   qeth: VLAN enabled
   qeth: Multicast enabled
   qeth: IPV6 enabled
   qeth: Broadcast enabled
   qeth: Using SW checksumming on hsi0.
   qeth: Outbound TSO not supported on hsi0
   qeth: Device 0.0.70fc successfully recovered!