Hello Intel888, I am sorry to hear you are having problems with your NUC and the AC7260 adapter.
First of all, I need to know which is the current BIOS version installed on your system? Please provide me with this information as soon as you can.
Could you test the Wireless adapter on another computer, in order to discard if it is defective?
It looks like the error code 28 is related to the chipset driver. So you could try to reinstall it again. Download Center
Once again thank you for your guidance in resolving my issue with AC7260 adapter not being detected by Window8.1. Once chipset driver was updated all was good now.
However, I do have one question;
1. Should I still upgrade the current Bios version 0021 - 10/17/2013?
Excellent! I’m glad to know you were able to resolve the issue.
Regarding the BIOS update, it is not necessary if the NUC is working fine.