However, it sounds like it's a technical accounting issue.
Only on a narrow definition. The reason the share price has fallen is the ominous words "revenue recognition". In software and services, it is very easy to adjust your turnover and profit by taking a long term contract or licence sale and choosing when you add the turnover and the profit to your results - either to pump up the latest results, or occasionally to defer to the next quarter or even year.
The real problem with revenue recognition that it lends itself to intentional fraud, usually by bringing forward future revenues and profits. The first time they do it, the directors always intend to sort it out next quarter, sweep it under the carpet, nobody will be any the wiser, nobody lost out. But if as a wide-boy CFO you chose to bring forward 3% of sales into the company's second quarter results to meet investor expectations, then (1) you've not really addressed whatever problem made you miss expectations, (2) next quarter you're already down by the amount you brought forward and you've got to make that up, and (3) your true starting point for the subsequent quarter is now lower than investors expect, but they expect the company to grow from the inflated figures reported.
In practice this means that what often starts out as a convenient interpretation of accounting rules to earn director bonuses then becomes a systematic fraud because in the subsequent quarter when the directors hoped to make good, for the reasons above they again miss expectations and have to bring forward more revenue, and the gap between true underlying results and what is reported starts to separate exponentially. This is primarily what happened at Nortel, Enron, Worldcom, Global Crossing, Satyam and many many others. That short list had reported assets of around $200bn when they filed for bankruptcy. I've worked for a company that collapsed in part due to revenue recognition fraud, the directors were crooks, but when they started making up the numbers they didn't intend to bankrupt the company or go to jail - but they did both.
As far as I know nobody is suggesting IBM will go bust, but with the ghost of Enron looking over their shoulder, investors are rightly spooked by a "revenue recognition" investigation. As it involves the US, UK and Ireland, my guess is that it is less about cheating overall corporate results, and more about "adjusting" the books to reduce the tax bill.