Hi,
Probably your problem is the return traffic. Because all your servers are in the same VLAN (IP Subnet) the traffic flow is:
Server -> VIP on ACE -> server
Server <----------------------- server.
To have loadbalancing working, your initial and return traffic both need to pass the ace, because it is a stateful device.
You can solve this by doing source NAT.
Take a llok at following example on how to configure SNAT.
http://www.cisco.com/en/US/products/hw/modules/ps2706/products_configuration_example09186a00809c3041.shtml
HTH,
Dario