After a number of denials, detailed reports on European exposure and more (including main investor Leucadia adding a substantial amount to their existing investment), Jefferies is still down nearly 10% today. Given the events of the day in Europe and the recent situation with MF Global, it becomes an instance of - as discussed earlier - loss of confidence. Jefferies can provide another and another (and another) explanation of its holdings, but if the market doesn't buy it, it's sell first and ask questions later (which can become a negative feedback loop.)
The firm has offered presentations of its levels of European exposure (see here and for greater detail here) and kept updating investors (see here), but while the stock has rebounded from the sudden 20% loss a few days ago, the market still seems to be unconvinced.
Rating agency Eagan-Jones is not budging from its downgrade of the firm recently, as present Sean Eagan discussed (or, better yet, argued with the CNBC anchors who sensed they weren't getting the positive take they wanted) in the clip below. Eagan also provides an excellent discussion of the European situation.