what about 401(k)s?

i had the infortunate circumstance of having to cash in my 401(k) to pay off expenses, including medical, before i moved to the uk. it was around $25,000.

how bad is this going to bite me in the ass?

Here is some info.

http://www.401kfocus.com/401k_questions.html#twentytwo

The $25,000 is entirely taxable at your US tax rate plus the 10% penalty, unless you meet an exception to the 10% penalty.

Because of the stacking rule introduced in 2006 for taxpayers claiming the foreign earned income/housing exclusions you may find that your marginal US tax rate for 2006 is higher than it would have been in previous years for others in the same circumstances.

So if your tax rate is 25% and the penalty is 10% you'll owe 35%...Youch!