Gwibber doesn't show Twitter messages anymore

Twitter messages don't show up in Gwibber anymore. How do I get them to show up again?

I've found the following error messages that have something to do with this issue:

When running 'gwibber-service' in the command line the following error messages appear:
2010-02-19 16:47:21,291 - <twitter:receive> Operation failed
2010-02-19 16:47:22,367 - <twitter:responses> Operation failed
2010-02-19 16:47:23,442 - <twitter:private> Operation failed

When running 'gwibber-service' in debug mode the following error appears in ~/.cache/gwibber/gwibber.log:
"error: (60, 'server certificate verification failed. CAfile: /etc/ssl/certs/ca-certificates.crt CRLfile: none')"