Strange deform/colander behaviour "string indices must be integers" - pyramid

Question

So I have the following working code, that I have been using for the past few months
class UserSchema(colander.MappingSchema):
dob = colander.SchemaNode(
colander.Date(),
title='Date of birth:')
if 'submit' in request.POST:
controls = request.POST.items()
try:
appstruct = myform.validate(controls)
except ValidationFailure, e:
return {'form':e.render(), 'values': False}
Now this is a basic date picker, as shown here:
http://deform2demo.repoze.org/dateinput/
But all of a sudden, when using this widget I get the error:
Traceback (most recent call last):
File "/home/luke/virts/pyramid-1.4.5/lib/python2.7/site-packages/pyramid_debugtoolbar-1.0.9-py2.7.egg/pyramid_debugtoolbar/panels/performance.py", line 55, in resource_timer_handler
result = handler(request)
File "/home/luke/virts/pyramid-1.4.5/lib/python2.7/site-packages/pyramid/tweens.py", line 21, in excview_tween
response = handler(request)
File "/home/luke/virts/pyramid-1.4.5/lib/python2.7/site-packages/pyramid_tm-0.7-py2.7.egg/pyramid_tm/__init__.py", line 82, in tm_tween
reraise(*exc_info)
File "/home/luke/virts/pyramid-1.4.5/lib/python2.7/site-packages/pyramid_tm-0.7-py2.7.egg/pyramid_tm/__init__.py", line 63, in tm_tween
response = handler(request)
File "/home/luke/virts/pyramid-1.4.5/lib/python2.7/site-packages/pyramid/router.py", line 161, in handle_request
response = view_callable(context, request)
File "/home/luke/virts/pyramid-1.4.5/lib/python2.7/site-packages/pyramid/config/views.py", line 347, in rendered_view
result = view(context, request)
File "/home/luke/virts/pyramid-1.4.5/lib/python2.7/site-packages/pyramid/config/views.py", line 493, in _requestonly_view
response = view(request)
File "/home/luke/pyramids/getwork2day.co.uk/getwork2day/views/signup.py", line 244, in user_signup
appstruct = myform.validate(controls)
File "/home/luke/virts/pyramid-1.4.5/lib/python2.7/site-packages/deform-2.0a2-py2.7.egg/deform/field.py", line 636, in validate
return self.validate_pstruct(pstruct)
File "/home/luke/virts/pyramid-1.4.5/lib/python2.7/site-packages/deform-2.0a2-py2.7.egg/deform/field.py", line 661, in validate_pstruct
cstruct = self.deserialize(pstruct)
File "/home/luke/virts/pyramid-1.4.5/lib/python2.7/site-packages/deform-2.0a2-py2.7.egg/deform/field.py", line 512, in deserialize
return self.widget.deserialize(self, pstruct)
File "/home/luke/virts/pyramid-1.4.5/lib/python2.7/site-packages/deform-2.0a2-py2.7.egg/deform/widget.py", line 1274, in deserialize
result[name] = subfield.deserialize(subval)
File "/home/luke/virts/pyramid-1.4.5/lib/python2.7/site-packages/deform-2.0a2-py2.7.egg/deform/field.py", line 512, in deserialize
return self.widget.deserialize(self, pstruct)
File "/home/luke/virts/pyramid-1.4.5/lib/python2.7/site-packages/deform-2.0a2-py2.7.egg/deform/widget.py", line 551, in deserialize
date = pstruct['date'].strip()
TypeError: string indices must be integers

Answer 1

At least dump current form controls to logging and post it here. Try to be more verbose & clear with your code examples and do not mix up colander schema code and pyramid view code.
if 'submit' in request.POST:
controls = request.POST.items()
try:
appstruct = myform.validate(controls)
except ValidationFailure, e:
log.debug('form validation fails for %r' % controls)
return {'form':e.render(), 'values': False}