Thank you for giving me the opportunity to assist you. I will give the best answer that I can with the information provided.
Hello there, if you withdraw from a converted Roth where you elected to spread out the income over 2011 and 2012, you may need to include more income in 2011, since the withdrawal will affect the amount of income to be reported in 2012 first.
The most that can be included in income because of the withdrawal of a conversion amount for any one year is the total amount required to be included in income for 2011 and 2012 minus the amounts included in income in all preceding years in the period.
For example, if you converted $10,000 in 2010, and are planning on reporting $5000 in 2011 and $5000 in 2012, ---and you want to withdraw $5000 in 2011, then you will need to report the entire amount as taxable in 2011.
See page 63 "later withdrawals from a Roth IRA" http://www.irs.gov/pub/irs-pdf/p590.pdf
Other than the tax on the income, there would be no additional penalty.