Not much to offer, I'm afraid. This seems to crop up on occasion for a very limited number of users for no reason I have been able to discern.Like earlier today: https://getsatisfaction.com/quickencommunity/topics/quicken-keeps-inserting-the-wrong-basis-for-shar...1 year ago: https://getsatisfaction.com/quickencommunity/topics/recording-a-stock-charitable-donation-the-added-...3 years ago: https://getsatisfaction.com/quickencommunity/topics/i-am-trying-to-fix-an-investment-account-that-sh...11 years ago: https://getsatisfaction.com/quickencommunity/topics/-92-quadrillion-cost-basisI have not reviewed in detail, but I suspect restoring a backup may still be the best option. You may need to go back farther. You might advise as to any changes recently made to Quicken or to OS setup.
I have the same situation for a new stock purchase of Johnson Controls. I deleted the downloaded transaction and entered it manually but get the same result.