HAHAHAHAHA, you still have MFNXQ in your account??? I wrote off my 50k investment in metromedia in 2003, sold the shares for just enough to cover commission. What a screw job that one was.
The stock is worthless, and you can write it off as such, whether or not it's in your account. In fact I'm surprised you waited so long, they went bankrupt in what 2003? The IRS won't challenge it, whether the shares are in your ameritrade account doesn't change the fact they're worthless.
Make a sell entry on your schedule, for the date put 12/31/06, and under sales price write WORTHLESS.
Print this out and include it with your return, the stock termination filing with the SEC
John Kluge should have been hung in a public square for the crap he pulled there, the company facing bankruptcy and he blows through 4 billion dollars in a little over two years. Bilked investors to the tune of 10 billion or so to build the network, then crashed the company into bankruptcy only to have him and his cronies scavenge the assets for pennies on the dollar.