I hit this as well, and solved it!
Two tips:
- It turned out the "only three columns" error was a red herring: the actual problem was that I thought these amounts should be cumulative, since other similar columns in form 2210 are cumulative. In fact they're not, and when I fixed that, the error went away.
- Next year buy TurboTax client software of the Online version. Not only does it allow you to edit the backing IRS forms manually ("Forms" view), the error reporting is slightly less cryptic than it is in the online version. It was when I was staring at the errors in the client software that I realized what the issue in #1 was.
