The U.S. dollar fell on Thursday, except against the yen, vacillating after data showed unexpected slowing in economic growth and an unwelcome inflation acceleration, potentially tying the Federal Reserve's hands on a pivot to easier interest rates.While the dollar was hardly shaken against the beleaguered yen, it otherwise only popped briefly after the Commerce Department reported that U.S. gross domestic product grew at a 1.6% annualized rate in the January-March period, slower than the 2.4% rate expected by economists polled by Reuters.The report also showed that underlying inflation as measured by the core personal consumption expenditures (PCE) price index rose 3.7% in the first quarter, eclipsing forecasts for a 3.4% rise.The inflation surprise puts an even greater-than-usual focus on the release on Friday of PCE price index data for March. The PCE index, and core PCE index factoring out food and energy prices are among the Fed's most important gauges of price behavior. Inflation remains stubbornly above the U.S. central bank's 2% inflation target.The yen, meanwhile, hit a fresh 34-year low versus the dollar and a 16-year low against the euro on Thursday as investors expect a Bank of Japan (BOJ) policy meeting that ends on Friday to not be hawkish enough to support the Japanese currency.