Oversized packets possibly causing packet loss with Dell PC6248

Hello,

We are seeing packet loss on our voice network which causes the phone to sometimes ring continuously.  This could be the result of oversized packets (more details below).  Also on a separate note, if I transfer images using Windows Deployment Service multicast it floods all ports (so I don't do that anymore :-).  I had originally enabled IGMP but it previously caused the switch to crash randomly which could have been related to earlier firmware.

We have pretty simple network:

1. 3 Dell PC6248s connected in a star topology (1 dist and 2 access switches) interconnected with LAG trunks running latest firmware.
2. Several VLANs: voice VLAN (100) for IP phones, production data is on vlan 1, dev on vlan 5.  
3. IP phones are mainly Aastra 9133i's with a few Polycom's.

I digged in further and we are seeing quite a few "oversized packets" on the LAG trunks.  I was wondering if this is causing the packets to drop.  If so, should I modify the MTU size to 1522 (I was reading that tagging adds 4 bytes to the default MTU of 1518) or is there a configuration error I'm overlooking somewhere?

1. • show rmon statistics port-channel 1
     
     Port: ch1
     Dropped: 0
     Octets: 3436040607  Packets: 947867566
     Broadcast: 1158102  Multicast: 24535676
     CRC Align Errors: 0  Collisions: 0
     Undersize Pkts: 0  Oversize Pkts: 43969059
     Fragments: 0  Jabbers: 0
     64 Octets: 24107589  65 - 127 Octets: 868940536
     128 - 255 Octets: 133380606  256 - 511 Octets: 76138498
     512 - 1023 Octets: 90380909  1024 - 1518 Octets: 72636117

   • show statistics port-channel 1
     
     Total Packets Received (Octets)................ 175230301131
     Packets Received > 1518 Octets................. 43968808
     Packets RX and TX 64 Octets.................... 24107385
     Packets RX and TX 65-127 Octets................ 868914890
     Packets RX and TX 128-255 Octets............... 133371613
     Packets RX and TX 256-511 Octets............... 76133886
     Packets RX and TX 512-1023 Octets.............. 90379490
     Packets RX and TX 1024-1518 Octets............. 72634059
     Packets RX and TX 1519-2047 Octets............. 4344763899
     Packets RX and TX 2048-4095 Octets............. 0
     Packets RX and TX 4096-9216 Octets............. 0
     
     Total Packets Received Without Errors.......... 947838588
     Unicast Packets Received....................... 922145059
     Multicast Packets Received..................... 24535481
     Broadcast Packets Received..................... 1158048
     
     Total Packets Received with MAC Errors......... 0
     Jabbers Received............................... 0
     Fragments/Undersize Received................... 0
     Alignment Errors............................... 0
     FCS Errors..................................... 0
     Overruns....................................... 0
     802.3x Pause Frames Received................... 0
     Unacceptable Frame Type........................ 0
     
     Total Packets Transmitted (Octets)............. 6732668920146
     Packets Transmitted > 1518 Octets ............. 5827795
     Max Frame Size................................. 1518
     
     Total Packets Transmitted Successfully......... 367499338
     Unicast Packets Transmitted.................... 4651719996
     Multicast Packets Transmitted.................. 5064125
     Broadcast Packets Transmitted.................. 5682513
     
     Total Transmit Errors.......................... 0
     FCS Errors..................................... 0
     Underrun Errors................................ 0
     
     Total Transmit Packets Discarded............... 0
     Single Collision Frames........................ 0
     Multiple Collision Frames...................... 0
     Excessive Collision Frames..................... 0
     
     802.3x Pause Frames Transmitted................ 0
     GVRP PDUs received............................. 0
     GVRP PDUs Transmitted.......................... 0
     GVRP Failed Registrations...................... 0
     BPDU: sent 1286910, received 9

Here's the config for our dist switch:

!Current Configuration:
!System Description "PowerConnect 6248, 3.3.6.4, VxWorks 6.5"
!System Software Version 3.3.6.4
!Cut-through mode is configured as disabled
!
configure
vlan database
vlan 5,10,15,20,25,50,100,150,200
vlan routing 1 1
vlan routing 5 2
vlan routing 100 3
exit
hostname "SW1-M01"
sntp unicast client enable
sntp server 192.168.0.211
clock summer-time recurring USA zone "CDT"
clock timezone -6 minutes 0 zone "CST"
stack
member 1 2
exit
ip address 192.168.150.250 255.255.255.0
ip address vlan 150
ip domain-name ***
ip name-server 192.168.0.211
ip name-server 192.168.0.212
logging 192.168.0.128
level warning
exit
ip routing
ip route 0.0.0.0 0.0.0.0 192.168.0.253
interface vlan 1
routing
ip address 192.168.0.254 255.255.255.0
exit
interface vlan 5
name "Dev_VLAN"
routing
ip address 192.168.10.254 255.255.255.0
exit
interface vlan 25
name "DSL_VLAN"
exit
interface vlan 100
name "Voice_VLAN"
routing
ip address 10.116.116.2 255.255.252.0
exit
interface vlan 150
name "Management_VLAN"
exit
username "admin" password ---- level 15 encrypted
voice vlan
line telnet
exec-timeout 1800
exit
ip ssh server
spanning-tree priority 4096
!
interface ethernet 1/g1
channel-group 1 mode auto
description 'SWI-M02_Uplink'
lldp transmit-tlv port-desc sys-name sys-desc sys-cap
lldp transmit-mgmt
lldp notification
lldp med confignotification
lldp med transmit-tlv location
lldp med transmit-tlv inventory
exit
!
interface ethernet 1/g2
channel-group 1 mode auto
description 'SWI-M02_Uplink'
lldp transmit-tlv port-desc sys-name sys-desc sys-cap
lldp transmit-mgmt
lldp notification
lldp med confignotification
lldp med transmit-tlv location
lldp med transmit-tlv inventory
exit
-- snipped due to length --

Thanks!