Turbo Tax keeps saying that the Payer's zip code on my 1099-R is invalid, but it's correct. What do I do?

if you imported it, delete it and enter it manually.  You can do this by going to the Review your 1099R Info screen and clicking on the trash can next the 1099R you are having trouble with.

Then re-enter the 1099R:

1. Select Add another 1099R at the bottom of the screen.
2. Continue to the financial institutions screen and select "Change how I enter my form"
3. Select "Type it myself"

Manually enter the information from the 1099R.  Make sure the amounts the 1099R entered are correct in TurboTax.

The form1099R represents amounts received from not only retirement accounts but from insurance contract and annuities also.  The information entered is matched by the IRS to what was reported on the 1099R.