Dell 6224 and Windows 2003 DHCP Server

Hi Experts,

Many thanks in advance. I got this problem that i can't figure it out and need your assistance or giving me some ideas. We inheritted an old network that  has a SonicWall 2040 connected to two Dell 6224s configured as stack unit. Port 1, 2, 3 are configured as vlan2. The rest of the ports configured vlan3.  Port 1 connected to the Sonic Wall, Port 2 connected to windows 2003 DHCP server. We have several building and each has its own vlan for security purposes. DHCP scope is configured on the windows 2003 server.

It seems we are having a problem with our internet so we suspected that old Sonic wall need a replacement. So, i put our Cisco PIX 515E to the task. From the dhcp server, because its default gateway pointed to the firewall, i can connect to the internet without any problem. However, clients stop receiving IP addresses as soon as I put the Cisco PIX515E on the network. Do you think this is something to do with the Dell vlan configurations? I removed the firewall CAT5 and DHCP server CAT5 to different vlan port and still, clients in different building don't receive ip addresses. When i put the sonicwall back to its original port, then, clients receive IP addresses.

Here is the switches running config, especially don't understand this command:

spanning-tree cost 20000
spanning-tree portfast

!Current Configuration:
!System Description "Dell 24 Port Gigabit Ethernet, 2.0.1.4, VxWorks5.5.1"
!System Software Version 2.0.1.4
!
configure
vlan database
vlan  2-10
exit
stack
member 1 1
member 2 1
exit
switch 1 priority 12
ip address 192.168.1.1 255.255.255.0
no diffserv
ip routing
ip route 0.0.0.0 0.0.0.0 10.0.0.1
bootpdhcprelay enable
bootpdhcprelay serverip 10.0.0.251
router rip
no enable
default-metric 1
exit
interface vlan 2
name "Internet - DHCP Server"
routing
ip address  10.0.0.2  255.255.255.0
exit
interface vlan 3
name "Bldg A"
routing
ip address  10.0.1.1  255.255.255.0
exit
interface vlan 4
name "Bldg B"
routing
ip address  10.0.2.1  255.255.255.0
exit
interface vlan 5
name "Bldg C"
routing
ip address  10.0.3.1  255.255.255.0
exit
interface vlan 6
name "Bldg G"
routing
ip address  10.0.4.1  255.255.255.0
exit
interface vlan 7
name "Bldg D"
routing
ip address  10.0.5.1  255.255.255.0
exit
interface vlan 8
name "Bldg M"
routing
ip address  10.0.6.1  255.255.255.0
exit
interface vlan 9
name "Bldg K"
routing
ip address  10.0.7.1  255.255.255.0
exit
interface vlan 10
name "Bldg F"
routing
ip address  10.0.8.1  255.255.255.0
exit

no spanning-tree
spanning-tree priority 4096
spanning-tree mst configuration
name "00-1C-23-5C-85-3E"
exit
router ospf
router-id 10.0.0.2
no enable
default-metric 1
default-information originate metric 1
exit
!
interface ethernet 1/g1
description 'Firewall'
spanning-tree cost 200000
spanning-tree portfast
switchport access vlan 2
exit
!
interface ethernet 1/g2
description 'Server'
spanning-tree cost 20000
spanning-tree portfast
switchport access vlan 2
exit
!
interface ethernet 1/g3
switchport access vlan 2
exit
!
interface ethernet 1/g4
switchport access vlan 3
exit
!
interface ethernet 1/g5
switchport access vlan 3
exit
!
interface ethernet 1/g6
switchport access vlan 3
exit
!
interface ethernet 1/g7
switchport access vlan 3
exit
!
interface ethernet 1/g8
switchport access vlan 3
exit
!
interface ethernet 1/g9
switchport access vlan 3
exit
!
interface ethernet 1/g10
switchport access vlan 3
exit
!
interface ethernet 1/g11
switchport access vlan 3
exit
!
interface ethernet 1/g12
switchport access vlan 3
exit
!
interface ethernet 1/g13
switchport access vlan 3
exit
!
interface ethernet 1/g14
switchport access vlan 3
exit
!
interface ethernet 1/g15
switchport access vlan 3
exit
!
interface ethernet 1/g16
switchport access vlan 3
exit
!
interface ethernet 1/g17
switchport access vlan 3
exit
!
interface ethernet 1/g18
switchport access vlan 3
exit
!
interface ethernet 1/g19
switchport access vlan 3
exit
!
interface ethernet 1/g20
switchport access vlan 3
exit
!
interface ethernet 1/g21
switchport mode trunk
switchport trunk allowed vlan add 4
switchport trunk allowed vlan remove 1
exit
!
interface ethernet 1/g22
switchport mode general
switchport general pvid 10
no switchport general acceptable-frame-type tagged-only
switchport general allowed vlan add 10
switchport general allowed vlan add 5 tagged
switchport general allowed vlan remove 1
exit
!
interface ethernet 1/g23
switchport mode trunk
switchport trunk allowed vlan add 6
switchport trunk allowed vlan remove 1
exit
!
interface ethernet 1/g24
switchport mode trunk
switchport trunk allowed vlan add 7
switchport trunk allowed vlan remove 1
exit
!
interface ethernet 2/g1
description 'Server'
switchport access vlan 3
exit
!
interface ethernet 2/g2
switchport access vlan 3
exit
!
interface ethernet 2/g3
switchport access vlan 3
exit
!
interface ethernet 2/g4
switchport access vlan 3
exit
!
interface ethernet 2/g5
switchport access vlan 3
exit
!
interface ethernet 2/g6
switchport access vlan 3
exit
!
interface ethernet 2/g7
switchport access vlan 3
exit
!
interface ethernet 2/g8
switchport access vlan 3
exit
!
interface ethernet 2/g9
switchport access vlan 3
exit
!
interface ethernet 2/g10
switchport access vlan 3
exit
!
interface ethernet 2/g11
switchport access vlan 3
exit
!
interface ethernet 2/g12
switchport access vlan 3
exit
!
interface ethernet 2/g13
switchport access vlan 3
exit
!
interface ethernet 2/g14
switchport access vlan 3
exit
!
interface ethernet 2/g15
switchport access vlan 3
exit
!
interface ethernet 2/g16
switchport access vlan 3
exit
!
interface ethernet 2/g17
switchport access vlan 3
exit
!
interface ethernet 2/g18
switchport access vlan 3
exit
!
interface ethernet 2/g19
switchport access vlan 3
exit
!
interface ethernet 2/g20
switchport access vlan 3
exit
!
interface ethernet 2/g21
switchport mode trunk
switchport trunk allowed vlan add 8
switchport trunk allowed vlan remove 1
exit
!
interface ethernet 2/g22
switchport mode trunk
switchport trunk allowed vlan add 9
switchport trunk allowed vlan remove 1
exit
exit