Si,
I'm pretty sure it's something to do with a Vag Code not a button combination or anything.
Apparently a lot of disks were stolen while the cars were being shipped hence the lock-down!
I had the same problem on my A4 Cab delivered in September. I read somewhere the DVD Sat Nav unit could play R2 DVD's so wanted to try it out. Couldn't take the sat nav disk out for the life of me. Around a month ago Audi UK offered a free firmware/hardware upgrade which involved activation of TMC (which is brilliant) and replacing the single DVD mapping with a double disk set (Western and Eastern Europe).
I popped over to my dealer and it was done while I waited. The tech also told me that 'eject' was now unlocked incase I wanted to use the other disk as part of my journey! Brilliant!
Got home, pushed eject. Nothing!!!
Not that bothered, will get them to look at it when I drive the Mrs over to pick up the Q7 next week.