Thanks for the reply. I'm sorry if I come across as a complete dummy regarding how things work, but I have barely started 'officially' using zen cart, and I admit I have a lot to learn. I wouldn't have come here if I knew what the problem was.
Anyway I double-checked my admin settings. The only shipping module I have installed is 'freeshipper' and that has shipping zones set to 'none'. My gift certificates are set as 'virtual - yes, skip shipping address' and all of my other products are digital downloads but set as 'no, shipping address required' as per every guide I've read for setting that up. I used the duplication method to set up all of my products so that I could keep consistent product settings.
I am so incredibly frustrated with this. I've made sales to people everywhere, including Texas. I don't want to just wave her off, but I'm at the point where I have NO idea what's going on with her ordering. I have not had this problem with anyone else, and I've had more than 200 orders in just a couple weeks.
I'm going to email her again and ask what she tried to order. All I can think of is I might have a product in there that has its settings messed up. If not, then I am completely lost as to what to do.
edit Ajeh, I'm sorry, I didn't see your reply until now. I was replying to Dr. Byte. I will check that out. That's a good idea. I swear I went through and double checked every single product to make sure the download attributes were attached, but it's possible I missed one. That's the ONLY thing I think could be causing this.