Thnx for quick reply!! Was already deinstalling to try the generic build :0)
Now retried and it indeed is working. Fyi: The 'middle button' on the 8700 is a quicklink. To insert content into fields use the space-bar, this does the swap to blank screen for input which returns after clicking scrollwheel and 'save'. So it seems like the space-bar is partially filling in the 'enter' and 'select' functions.
Managed to crash it also: got an exception on 'mailqueue too long'. (maybe because my inbox contains almost 10.000 messages unread, still testing our own domain and preparing for migration

)
Anyway: beta looks very promising!!