Twitter spam filter started to block Bit.ly links.
Approximately 11 hours ago have Twitter API started to reject statuses with Bit.ly links as malware. We have reported this error to the Twitter team and now we’re waiting for their response.
For the time being we suggest you to temporarily switch to fplus.me link shortener or use Bit.ly with custom domain.
UPDATE: Twitter fixed it. It’s ok to use bit.ly shortener again.
Thank you for your patience.