I downloaded the PCResale Customer Database zip file that is linked on the B5 lesson page (this page) and extracted it to a folder in my Documents. After following along the lesson to about minute 10, when we added credit limit to the query, I found that the credit limit field was displaying as a date.

I inspected the SQL code, the format of the CreditLimit field, the format of the column in the datasheet view (which was correct), and I tried making the query from scratch, and could not find the cause of the problem or work around it.

Eventually I re-downloaded the PCResale database and no longer had the problem. I would hate for this to happen to a database I spent a lot of time on. Copying the database did not fix the problem, so it seems likely that this could occur without my knowledge while I was working and be saved as a backup, leaving me with a broken backup. Any idea what caused this? I can keep doing the lesson since I was able to download a second, working copy, but I would love to know how to fix the problem.