Bitcoin can’t get a breather. First Mt. Gox imploded. Now, Flexcoin has flatlined. The Alberta, Canada-based Bitcoin exchangesays its closing down after cyber thieves made off with about $600,000 worth of the digital currency. Thanks to a “front-end flaw” in Flexcoin’s software code, hackers ripped off all 896 of the small trading post’s modest supply of bitcoins. Flexcoin launched in June 2011 on an invite-only beta basis and officially went live on Aug. 4 later that same year.