You have a few options at this point:
1. Contact the 1099-Misc payer and ask to correct the form; the corrected form is then reported to the IRS and you'll only have to report 1099-B.
2. If 1099-MISC is not corrected - report only 1099-B, print and mail the tax return with attached explanation why 1099-MISC is not reported and could not be corrected (be sure to mention you contacting the payer and requesting the correction). The IRS has the form 1099-MISC and will be looking for it on your tax return. To avoid their summer correspondence, detailed explanation may accomplish just that.
3. The last option is to report both. However, when reporting form 1099-MISC as income, you would have to enter the same amount as a negative amount in Other Miscellenous income. Although it is not an ideal solution, the negative amount will "zero out" the amount and you won't be double taxed and the 1099-MISC is reported for the IRS matching purposes. To do that, go to Federal Taxes and
choose Wages and Income. Scroll down to Less Common Income and
choose the last category, Miscellaneous Income. On Let's Work on Any Miscellaneous Income,
choose the last category, Other reportable income. Continue to the screen Other Taxable Income.
Enter the description and a negative amount for 1099-MISC.
