Jumbo Frames not working ESXi 4.1 on ML350 and HP2910al

Ok so I have two HP ML350 G6 servers connected to two HP2910al switches using iSCSI, I have followed the instructions for setting the MTU on all the vswitches and esxcfg-vswitch -l gives the following output:

~ # esxcfg-vswitch -l
Switch Name      Num Ports   Used Ports  Configured Ports  MTU     Uplinks
vSwitch0         128         8           128               9000    vmnic1,vmnic2

  PortGroup Name        VLAN ID  Used Ports  Uplinks
  Management Network    0        1           vmnic1,vmnic2
  Virtual Machines      0        4           vmnic1,vmnic2

Switch Name      Num Ports   Used Ports  Configured Ports  MTU     Uplinks
vSwitch1         128         5           128               9000    vmnic3,vmnic0

  PortGroup Name        VLAN ID  Used Ports  Uplinks
  iSCSI_1               0        1           vmnic0
  iSCSI_2               0        1           vmnic3

Switch Name      Num Ports   Used Ports  Configured Ports  MTU     Uplinks
vSwitch2         128         4           128               9000    vmnic4

  PortGroup Name        VLAN ID  Used Ports  Uplinks
  Windows iSCSI         0        1           vmnic4
  VMkernel              0        1           vmnic4

The HP2910 switches are both set to use an MTU of 9000, the HP "show vlans" command gives the following output:

ProCurve 2910al-24G Switch# show vlans

Status and Counters - VLAN Information

  Maximum VLANs to support : 256
  Primary VLAN : DEFAULT_VLAN
  Management VLAN :

  VLAN ID Name                 | Status     Voice Jumbo
  ------- -------------------- + ---------- ----- -----
  1       DEFAULT_VLAN         | Port-based No    Yes
  2       DataLAN              | Port-based No    No

ProCurve 2910al-24G Switch#

if I use vmkping -s 8972 a.b.c.d from an ssh session to the host I get a timed out error

if I just use vmkping (without the -s switch) I get all three packets back

if I ping using the data-size switch from the 2910 I get a timed out error

if I do a straight ping I get the packet back

Any ideas, the switch is directly connected to this esx host.

many thank

Update:

I can ping between other SAN devices from the switches using ping data-size 8792 xxx.xxx.xxx.xxx

I can ping between nics if I don't use jumbo frames i.e. vmkping xxx.xxx.xxx.xxx is OK, but if I use a jumbo frame it times out i.e.

vmkping -s 8792 xxx.xxx.xxx.xxx times out.

This would suggest a problem with the nic or the vswitch setup, the nics are two HP NC360T's

all ideas, tips and suggestions welcome 'cause I am stuck now.

Ian