1099-R Taxable amount different on TT calcs

Did you enter the 1099-R as written on the form ?  Was the box 2b checked ?  I would delete the 1099-R and reenter it manually  and do not check box 2b this time ... that way the program will accept the taxable 2a amount. 

It's odd that the Form 1099-R would have only $2,900 in box 2a when there is $0 in box 5 (unless the Form 1099-R has code 8, P or E in box 7, although with any of these codes there is no way to cause TurboTax to determine the taxable amount to be anything other than the amount in box 2a).  I would expect this Form 1099-R to have the amounts in boxes 2a and 5 that sum to the $42,000 in box 1.  I would ask the payer how they determined that less then the full amount is taxable and why the difference is not present in box 5.