Just over three months after its last funding round, European fintech giant Klarna is announcing today that it has raised another $639 million at a staggering post-money valuation of $45.6 billion. Rumors swirled in recent weeks that Klarna had raised more money at a valuation north of $40 billion. But the Swedish buy now, pay later behemoth and upstart bank declined to comment until now. SoftBank’s Vision Fund 2 led the latest round, which also included participation from existing investors Adit Ventures, Honeycomb Asset Management and WestCap Group. The new…