Warner Music ( WMG) plunged 19% early Thursday after a European court blocked a merger of rival music companies. The European Commission had approved the 2004 merger of Sony Music and BMG, but a court on Thursday threw out that decision, forcing European regulators to take a new look at the deal. The news sent Warner into a tailspin because the company's shares have been bolstered in recent months by news of merger talks with London rival EMI. But merger discussions between EMI and Warner are likely to be suspended in light of the court decision, Reuters reported Thursday, citing sources. Early Thursday, Warner slid $3.96 to $25.80.