there is a new rear wiper blade assembly for early model X-5s. it it stronger and solves the replacement hassle. costs around $60-70. :)

If you dont want to mess about replacing the rubber, then just buy a new wiper blade from your local stealer, this is what I did. cost me £10 GBP and was dead easy to change. The blade (incl metal support) just pushes DOWN towards the screen (when you have the blade arm lifted as in your pic). Then just do the reverse to fit your new BMW blade.