I can't import workflows from file on a freshly installed instance of Galaxy on Amazon Cloud. The error message is copied below. Do you have some idea on how to fix this?

Thanks,

Sébastien

Internal Server Error
Galaxy was unable to sucessfully complete your request
URL: http://ec2-50-19-79-199.compute-1.amazonaws.com/workflow/import_workflow
Module galaxy.web.framework.middleware.error:149 in __call__
>>  app_iter = self.application(environ, sr_checker)
Module paste.recursive:84 in __call__
>>  return self.application(environ, start_response)
Module paste.httpexceptions:633 in __call__
>>  return self.application(environ, start_response)
Module galaxy.web.framework.base:132 in __call__
>>  return self.handle_request( environ, start_response )
Module galaxy.web.framework.base:190 in handle_request
>>  body = method( trans, **kwargs )
Module galaxy.webapps.galaxy.controllers.workflow:1127 in import_workflow
>>  workflow, missing_tool_tups = self._workflow_from_dict( trans, data, source=src,add_to_menu=add_to_menu )
Module galaxy.webapps.galaxy.controllers.workflow:1823 in _workflow_from_dict
>>  module = module_factory.from_dict( trans, step_dict, secure=False )
Module galaxy.workflow.modules:428 in from_dict
>>  return self.module_types[type].from_dict( trans, d, **kwargs )
Module galaxy.workflow.modules:222 in from_dict
>>  module.state.decode( d[ "tool_state" ], module.tool, module.trans.app, secure=secure )
Module galaxy.tools:849 in decode
>>  self.inputs = params_from_strings( tool.inputs, values, app, ignore_errors=True )
Module galaxy.tools.parameters:92 in params_from_strings
>>  value = json_fix( from_json_string( value ) )
Module simplejson:384 in loads
Module simplejson.decoder:402 in decode
TypeError: expected string or buffer