Soap fault on vmdk creation

I want to create a vmdk on my datastore so I attempted this

1. sub atomicAddDisks{
2.   # Getting the views
3.   print"DEBUG : GETTING CONTENT\n";
4.   my$content= Vim::get_service_content();
5.   my$VDiskManager= Vim::get_view(mo_ref =>$content->virtualDiskManager);
6.   my$diskSpec= VirtualDiskSpec->new(
7.     adapterType =>"ide",
8.     diskType    =>"thin"
9.   );
10.   print"DEBUG : CREATING VDISK\n";
11.   $VDiskManager->CreateVirtualDisk_Task(name =>"[zebi1n]helloworld.vmdk", spec =>$diskSpec);
12.   print"DEBUG : AFTER VDISK\n";

As you can see, I hardcoded the path for debugging but I get a very unhelpful SOAP error

SOAP Fault:

-----------

Fault string:

Fault detail: InvalidArgumentFault

Does anyone know what is going on?