installing windows7 on proxmox 1.8

Hi,
can somebody help me with this :(
im using proxmox 1.8 and already installed windows7 as a virtual machine, my problem is that my windows 7 cannot ping its gateway or our office network

proxmox settings (static)
IP: xx.xx.26.248
netmask: 255.255.248.0
gw: xx.xx.24.1

windows 7 settings (static)
IP: xx.xx.26.249
netmask: 255.255.248.0
gw: xx.xx.24.1

heres the situation:
1. my proxmox can ping our network here in the office (no problem)
2. windows 7 (my VM) can ping my proxmox(xx.xx.26.248)
3. windows 7 cannot ping its own gateway (xx.xx.24.1)
4. windows 7 cannot ping our network in the office
5. from our office network, I can ping proxmox(xx.xx.26.248) but not windows7 IP(xx.xx.26.249)
6. in my proxmox web windows7 settings, i am using rtl8139 then vmbr0
7. in my proxmox command settings under /etc/network/interfaces
auto lo
iface lo inet loopback
iface eth0 inet manual
iface eth1 inet manual
auto vmbr0
iface vmbr0 inet static
address xx.xx.26.248
netmask 255.255.248.0
gateway xx.xx.24.1
bridge_ports eth0
bridge_stp off
bridge_fd 0


please help me :(
thanks in advance