HP MSM422 Access Points and HP Controller

We have multiple clients utilizing MSM422 Access points and a handful of HP Controllers.  For this email, we will say MSM710 controllers.  When we are at clients that are using all HP Equipment, we put the APs in a trunk port, they are able to connect to the DHCP Server via a helper address and they pull an IP Address on the HP Wireless VLAN(Separate VLAN) and they connect to the controller and pull down their configuration.  Everything works flawlessly and they configure themselves within a couple of minutes.  

Now, on our clients that are running Cisco networks, we hook everything the same way.  However, the MSM422's seem to randomly grab different DHCP Addresses from random DHCP Scopes.  It is as though it just grabs a vlan off the trunk and just grabs an ip address.  Sometimes we are lucky and it grabs off the correct VLAN but it is extremely random.  We thought we can solve this by setting DHCP Reservations and that increased the percentage of working correctly on Cisco equipment from 10% to about 50%, but we still have problems.  

So, my question is, does anybody use the HP APs and controllers on a cisco network?  If so, did you find any special tricks to get it to grab a good ip on the wireless vlan as well as configure itself correctly off the controller?  

Thanks for your help.

Joe R.