This is backup withholding. It sounds like you missed checking the box on the W-9 saying you weren't subject to it. Here's a link with more explanation:
http://www.irs.gov/taxtopics/tc307.html
Are you a US citizen? Did you fill out a w9?
I don't know if you're asking me or the OP, but I don't recall filling the W9 out. I opened the account years ago, but they only started withholding the federal taxes several months ago.
And yes, I am a US citizen, born and raised.