Even if specified else, all my VMs end up with 768MB memory. Using ESX 5 with the vmware branch of november 15th 2012.

The post to foreman seems fine:

Started POST "/compute_resources/1-myesx/vms" for 192.168.56.1 at Thu Nov 15 11:04:17 +0100 2012
  Processing by ComputeResourcesVmsController#create as HTML
  Parameters: {"vm"=>{"name"=>"foreman_1352973844", "path"=>"Datacenters/DC1/vm", "volumes_attributes"=>{"new_volumes"=>{"name"=>"Hard disk", "_delete"=>"", "datastore"=>"ESX2 SAS", "size_gb"=>"10"}, "0"=>{"name"=>"Hard disk", "_delete"=>"", "datastore"=>"ESX2 SAS", "size_gb"=>"10"}}, "cpus"=>"1", "memory"=>"4294967296", "interfaces_attributes"=>{"0"=>{"_delete"=>"", "network"=>"Intern"}, "new_interfaces"=>{"_delete"=>"", "network"=>"Intern"}}, "start"=>"1", "cluster"=>"AICD"}, "commit"=>"Save changes", "compute_resource_id"=>"1-myesx", "utf8"=>"✓", "authenticity_token"=>"token"}
Redirected to http://192.168.56.104:3000/compute_resources/1-myesx/vms
Completed 302 Found in 2887ms