Hangs when adding a document

[Evan]

When I try to add a document (from a file, pasting bibtex, or just doi) referencer will hang looking up bibliographic information. I've attached a backtrace from all threads.

Steps to repropduce
1. Documents > Add reference with id
2. paste "http://dx.doi.org/10.1016/j.ress.2006.07.001"
3. click OK.

Result
Referencer hangs (window turns gray). The tail of the console output is:

bool PluginManager::resolveMetadata(Document&):
 PluginManager::resolveMetadata: paydirt with module 'crossref'
Glib::ustring Document::getField(const Glib::ustring&):
 Document::getField: WARNING: unknown field bibsource
void referencer_document_dealloc(PyObject*):
 >> referencer_document_dealloc
bool PluginManager::canResolve(Document&):
 PluginManager::canResolve found module 'dblp'

ProblemType: Bug
DistroRelease: Ubuntu 13.10
Package: referencer 1.2.1-1
ProcVersionSignature: Ubuntu 3.11.0-14.21-generic 3.11.7
Uname: Linux 3.11.0-14-generic x86_64
NonfreeKernelModules: nvidia
ApportVersion: 2.12.5-0ubuntu2.1
Architecture: amd64
Date: Thu Dec 19 14:48:08 2013
InstallationDate: Installed on 2011-08-29 (842 days ago)
InstallationMedia: Ubuntu 11.04 "Natty Narwhal" - Release amd64 (20110427.1)
MarkForUpload: True
SourcePackage: referencer
UpgradeStatus: Upgraded to saucy on 2013-10-21 (59 days ago)