Received the same call.  It is a scam.  There is a warning posted on the US Treasury website.

I was 100% sure that it was a scam as I deal with this in the business world a lot.  Although I didn't realize how unnerving it would be to get one personally.   I can't image how it affects older people.

I received a phone call from phone number, instructed to call back the same phone number and ask for "exchange 105".  Very broken english and when asked, said they meant extension.  I called the number and asked for ext 105, sounded like very same voice (I asked for a name and was told it was Dwayne Maguire) that called and told me that they need my lawyer to call them.  I asked why I would need a lawyer and they said that I filed my 2008 taxes incorrectly.  I told them that the IRS would contact me, not the US Department of Treasury with a letter to straighten out and then I was told that I would be arrested and put in jail for six months.  As I again asked why I needed a lawyer as I believed this to be a scam, they hung up on me.

Received threatening call from Department of Legal Affairs stating legal action had been started against me... Nice try. I rate this as a SCAM

I just got the exact same message but it was from Andy Parker.