You need to enter the relevant data for the Child and Dependent Care credit under Deductions and Credits...or do a Search (upper right for 2441 and click on the jump-to link (Mac users must find it in the Topics List).
You have to show that you had child care expenses and you have to show that both spouses had earned income (or one was disabled and/or a full-time student).
If not, then the amount in box 10 contributed to the dependent care FSA is added back to your income.
So did you do the Child and Dependent Care credit interview? Did you go all the way through it? Do both spouses have earned income?
Make sure both W-2s are entered BEFORE you start the Dependent Care Credit Section. Normally, the Dependent Care Credit Section should ask you about your daycare expenses, but I think if both W-2s aren't entered before this is started, I wonder if Turbotax assumes someone isn't working and won't let you fill this section out (thus thinking box 10 is taxable)? Try deleting the Dependent Care Credit (Form 2441) section after both W-2s are filled out and re-enter your information and see if it asks you for your daycare expenses and fixes the issue?