ahead of G20 and IMF meetings later this month. As to the epidosde at UBS, Silva, the analyst, outlined three possible ways a loss that big could take place: intentional fraud, basic stupidity in trading strategy, or what the banking industry calls fat fingers, which means typing the wrong number by accident. Perhaps the trader put in an extra zero so instead of buying a million he or she bought ten million -- could be a problem, Silva said. Lex van Dam, a former trader who is now a partner at Hampstead Capital in London, said chaos in the markets could have put more pressure on a trader desperate to hang onto his job. Trading has been incredibly difficult over the last year, said van Dam. With the volatility in banking stocks, commodities and currencies, things can go wrong really, really easily. If you 're worried about your job and you try to hide -LRB- a mistake or loss -RRB-, you can see how these situations arise. A bank's risk management division is supposed to examine a trader's activities, he said. He must have done something that he was n't supposed to do, obviously, van Dam said. UBS said no client positions were affected by the loss, which is still being investigated. But the unauthorized trading by a trader in its investment bank could cause UBS to post a loss in the third quarter of this year, it said. The loss would potentially be among the largest costs ever