I should have added that they didn't update their guidance in December, 2011, which was what other semiconductor companies were doing, nor did they warn when they issued their PR announcing yesterday's CC.
Usually, that means that a company has achieved results within the existing guidance. In Ixys' case, that would have meant revenue roughly in the range of $92M - $96M.
The market may even have anticipated that, like the the other semiconductor companies that have recently reported, Ixys would see a lower Q4 (March quarter,) due to impact from Europe and the flooding in Thailand.
All of that was probably priced into yesterday's close.
A $12M miss from the low end of the guidance was not expected.