I have had a few users telling me they were having problems both contacting me, and using the SBST. One user narrowed it down to undisposable.net, and I stupidly didn't think to check the site myself at the time.
Checking undisposable.net today shows the site is offline. It's still resolving to 18.104.22.168, but no content is there, so it's failing to connect. There's no contact information in the WhoIs for the site so I've no way of contacting the sites owner to find out whats going on.
Until the site is back, those of you using the Spambot Search Tool should disable the undisposable.net check by changing the following in config.php;
$bBlockDisposable = TRUE; // undisposable.net
$bBlockDisposable = FALSE; // undisposable.net