SpinnerRow, We have received some comments from customers reporting audio issues when using an AV receiver and HDMI. The following forum will give you additional information on this https://communities.intel.com/message/218663#218663
Then, in regards to the operating system let me inform you that this specific NUC support Windows 7, Windows 8 and Windows 8.1 64-bit only. We have received comments from customers reporting compatibility with Linux flavor OS, however Intel has not validated them.
The following link contains the latest graphics drive available; however it is for Windows 64bit operating system.
If you continue having issues you can always contact our technical support team for additional troubleshooting. http://www.intel.com/p/en_US/support/contactsupport
At this point the only way to find out if the NUC is defective will be by installed a supported operating system and check if the behavior persisted.
If it does, you may contact our warranty department so they can help you replacing the product.
Please check the following link for additional support on Linux