To respond to some comments:
-I've been doing our taxes myself for years (using some online tax prep sites - TurboTax, etc.). I pull together all the documents and all the rest. So I do have some understanding of how the 1040 works. I've also had to do Schedule C's for my self-employment income. We've never had a problem.
-Once the conversion is done, it can't be reversed. However, when we talked with someone from Vanguard, they said there is some question about whether their user interface is flawed (direct quote: "you aren't the first person who has done this, and you won't be the last"), and it is certainly clear what our intent was. Their website has gotten even more confusing lately, and I could have sworn the number we entered was the dollar amount and not shares, but something weird happened, apparently. We are still waiting to hear what they are willing to do. They didn't give us an outright "no," and as I said above, the accountant we consulted thought it was quite possible they would reverse this.
-We cannot contribute to our IRAs anymore because we don't receive taxable compensation anymore (except for my very small self-employment income). We both moved our tIRA funds to rollover IRAs a while back.
-I do wish we had not bothered with these Roths (now!), but the idea was to have some funds we could draw on in the future if we needed a larger amount for something (like real estate, or a medical emergency) without having to worry about taxes.
-What we (especially DH) are worried about is that if this conversion stands, we will have a very large taxable income for this year that will bump us up to the highest tax bracket, and no matter how we pay the tax it will take an extra chunk out of our net worth (vs. if we had taken the money out in smaller installments over time, as we had planned). It's not like we have LOST this money; it's sitting there earning interest tax-free as we type. My reasoning is that even if we do have to pay this tax bill, we can do it over some period of time (say, a year), and it might all work out not too badly in the end. If that's the case, we'll certainly consult a professional (CPA, preferably an enrolled agent).