CoreWeave's valuation has tumbled in recent months, and that could put a key acquisition at risk.This year, CoreWeave (CRWV 0.39%) joined the list of hot new artificial intelligence (AI) stocks to buy. The company's close partnership with chipmaker Nvidia made it appear to be a fairly safe way to invest in AI, and its valuation has tripled since it went public back in March.In the past three months, however, the price of this AI stock has fallen by around 26% (returns as of Sept. 17). One reason for the pri ...