Thanks so much for your help. Since I posted my question, I have learned more, so if you're interested (And I hope you are!) here are the details.
First, yes, I tried deleting and re-importing the data, but it is still showing exactly double the correct adjustment. The problem seems to be related to a problem experienced by many others who have downloaded data from E*Trade after the conversion to Morgan Stanley. Each of the thousands of sales in the detailed data has an adjustment code of "N", which apparently is not a valid adjustment code. And, in particular, it is not the adjustment code that should be used for disallowed wash sales. So the disallowed wash sales come from the summary totals in the 1099-B form, and the adjustments with the invalid "N" code (which include all the wash sale adjustments) are being added up and included in the total adjustment. This is how the adjustment is getting doubled. It all boils down to a crapload of detailed data records with incorrect adjustment codes. It really looks like a data problem from ETrade / Morgan Stanley.
Thanks for reading this to the bitter end!
