The accusation that the CEO was under tax evasion investigations came from a former reporter for a Chinese magazine. The accusation was made on her personal blog, and was then denied by Foxconn (whose parent company is Hon Hai) as "a bunch of nonsense." There may be a reason to believe them.
These charges do seem a bit strange when you look at them for more than 10 seconds. The woman claims that the IRS demands the (up to) $1.49 billion worth be paid up, plus a fine of up to three times that amount. And it gets even stranger when you consider that the same reporter was found guilty of blackmailing the CEO for $1 million, and was sentenced to a year and ten months. [Chinapost - Thanks Ben!]