Updated from 2:09 p.m. EDTBank of America ( BAC) proved on Monday that it didn't merely return to profitability last quarter -- it soared. However, when one-time items, preferred dividend payments and unusual gains are stripped out of the whopping $4.2 billion profit BofA reported, the picture becomes significantly bleaker. On a conference call, BofA executives predicted a few more quarters of strained credit conditions before the economy starts to improve -- a forecast that doesn't bode well for core banking operations. And investors began to realize that booming profits reported of late by financial powerhouses, which sparked a major market rally, may not be hardy enough to sustain it. Bank of America shares plunged 24.3% to $8.02 at the close Monday, its low for the day. The firm was among the biggest drags for the market, along with other financial stocks like Citigroup ( C), Wells Fargo ( WFC) and JPMorgan Chase ( JPM). The Dow Jones Industrial Average closed down 3.6%. BofA blew away Wall Street expectations on Monday, reporting a first-quarter profit attributable to common shareholders of $2.8 billion, or 44 cents per share. The figure was 11 times the average analyst estimate of 4 cents per share, according to Thomson Reuters. Excluding preferred dividend payments, the Charlotte, N.C.-based company would have earned $4.2 billion. During the same period a year ago, BofA posted a $1.2 billion profit, or 23 cents per share.