Yep, same "Nicki Johnson from the IRS" scam (exact same recording except for the phone number to call back) as I received three days ago from 408-418-0210. Scam. The first contact from the "real" IRS will ALWAYS be by US Postal Service (regular mail), and it will contain details of exactly what they are looking at (year of your tax return in question, dollar amounts, etc.). And it's not time-critical, you don't have to contact them "the very second you receive this message", as Nicki directs you to. For more information, (and to report this to the IRS) see the posting from Slim on this site under the 408-418-0210 number.
"I am officer Nicki Johnson from the Internal Revenue Service and the hotline to my division is #########. Don't disregard this message and do return this call before we take any action against you. Good bye and take care"