I have the Microsoft Entertainment Centre 8000 and it works great but I did have to buy a new Belkin Bluetooth adapter for mine to work properly. But now for no apparent reason the 'Z' key decided to jump off. I have the key and the little rubber cone that goes under it but for the life of me I can't get it to clip back on. Can someone tell me how to fix it. Many thanks, Lorraine

SOURCE: I have a Microsoft Wireless Entertainment Keyboard

My MS dontle gave me nothing but problems, now I have two Belkin Bluetooth dongles, one covers a 10 metre range and is for a USB 1.1 connection, the latest one a 100 metre range USB 2 one.
The first one worked fine but thinking that my machine only has USB 2 sockets I installed the new 100 metre range one thinking it would be much better, but it wasn't it froze and had jerky movements so I came to the conclusion that it was picking up interference from someone mobile or computer.
So I ended up going back to the first one and it works great.
Try a friends Bluetooth dongle and see if it works better than the one you got with your keyboard, it might cure your problem as mine did.
You can get them for pennies on eBay.

SOURCE: i need a new dongle as i broke mine, did buy a

You can order replacement parts directly from Microsoft.

U.S. Customers can contact the Microsoft Order Desk at: (800) 360-7561 (Monday through Friday, 8:00 a.m. to 7:00 p.m. Eastern Standard Time)

SOURCE: I have a microsoft wireless entertainment desktop

Try looking in your bluetooth places and see if you can add the keyboard by itself, if not remove the mouse/keyboard and try re-adding them both as a pair.

SOURCE: MS Wireless Entertainment Keyboard 8000 - FN keys not working!

There is probably a function lock or "F-Lock" button. This works just like caps lock, or num lock. Turn off the Function Lock if you have one, and see if that solves your problem.