I just came across this issue today again:

https://bugs.launchpad.net/maas/+bug/1446915

=> /var/log/maas/regiond.log <==
2015-04-27 15:08:53 [-] 127.0.0.1 - - [27/Apr/2015:15:08:52 +0000] "GET /MAAS/metadata//2012-03-01/user-data HTTP/1.1" 200 3439 "-" "python-requests/2.2.1 CPython/2.7.6 Linux/3.13.0-35-generic"
2015-04-27 15:08:55 [-] 127.0.0.1 - - [27/Apr/2015:15:08:54 +0000] "GET /MAAS/api/1.0/nodes/?nodes=node-a0754dc0-c4cd-11e3-824b-00163efc5068&op=deployment_status HTTP/1.1" 200 64 "-" "Go 1.1 package http"
2015-04-27 15:08:58 [-] 127.0.0.1 - - [27/Apr/2015:15:08:58 +0000] "GET /MAAS/api/1.0/nodes/?agent_name=a4a9be1b-5c0a-424d-81d7-35a43d9478b1&id=node-a5224922-ae98-11e3-b194-00163efc5068&op=list HTTP/1.1" 200 2 "-" "Go 1.1 package http"
2015-04-27 15:08:59 [root] ERROR: 
Traceback (most recent call last):
  File "/usr/lib/python2.7/dist-packages/django/core/handlers/base.py", line 112, in get_response
    response = wrapped_callback(request, *callback_args, **callback_kwargs)
  File "/usr/lib/python2.7/dist-packages/maasserver/api/support.py", line 52, in __call__
    response = upcall(request, *args, **kwargs)
  File "/usr/lib/python2.7/dist-packages/django/views/decorators/vary.py", line 19, in inner_func
    response = func(*args, **kwargs)
  File "/usr/lib/python2.7/dist-packages/piston/resource.py", line 167, in __call__
    result = self.error_handler(e, request, meth, em_format)
  File "/usr/lib/python2.7/dist-packages/piston/resource.py", line 165, in __call__
    result = meth(request, *args, **kwargs)
  File "/usr/lib/python2.7/dist-packages/maasserver/api/support.py", line 200, in dispatch
    return function(self, request, *args, **kwargs)
  File "/usr/lib/python2.7/dist-packages/maasserver/api/nodes.py", line 412, in start
    node.start(request.user, user_data=user_data)
  File "/usr/lib/python2.7/dist-packages/maasserver/utils/orm.py", line 399, in call_within_transaction
    return func_within_txn(*args, **kwargs)
  File "/usr/lib/python2.7/dist-packages/django/db/transaction.py", line 339, in inner
    return func(*args, **kwargs)
  File "/usr/lib/python2.7/dist-packages/maasserver/models/node.py", line 1920, in start
    claims = self.claim_static_ip_addresses()
  File "/usr/lib/python2.7/dist-packages/maasserver/models/node.py", line 1742, in claim_static_ip_addresses
    alloc_type=alloc_type, requested_address=requested_address)
  File "/usr/lib/python2.7/dist-packages/maasserver/models/macaddress.py", line 358, in claim_static_ips
    interface, alloc_type, requested_address, user=user)
  File "/usr/lib/python2.7/dist-packages/maasserver/models/macaddress.py", line 247, in _allocate_static_address
    user=user)
  File "/usr/lib/python2.7/dist-packages/maasserver/models/staticipaddress.py", line 179, in allocate_new
    alloc_type, user, hostname=hostname).wait(30)
  File "/usr/lib/python2.7/dist-packages/crochet/_eventloop.py", line 217, in wait
    result = self._result(timeout)
  File "/usr/lib/python2.7/dist-packages/crochet/_eventloop.py", line 195, in _result
    raise TimeoutError()
TimeoutError

I also came across: https://bugs.launchpad.net/maas/+bug/1379370 ... I wonder if there's something related there?