Most people that use SpearNZB and other applications that use TheTVDB have noticed that it's been up and down for the last couple of weeks.
It's possible that it's not scaling to the load being put on it, and they are also in the process of moving it to another server.
Since version 1.0.3 I've been developing my own TV database that combines information from TheTVDB and TVRage that will scale to whatever the load becomes.
What has slowed this down is the uptime of TheTVDB along with some significant changes to the app along with writing a sync utility.
I hope to have a new version out soon.....
Thanks,
Kraig