Urgent! Do I have to pay self-employment tax?

Created a sole member LLC 2010 to manufacture and sell bioreagents for medical research labs.  Profit for 2010 is 150K.  Sent myself a 1099-MIS and files tax return as independent contractor without claiming self-employment tax.  Last week received a letter from IRS, asking adjustment of self-employment tax plus penalty.  Do I have to pay self-employment tax?  I got confused.  My friend told me that I do not need to file self-employment tax 'cause I received a 1099-MIS and can be treated as an independent contractor.  Can someone in this forum help m out by replying this post?  Many thanks!!!