Pull the blind up totally(to its very maximum), very very very gently and straight with your both hands, one on the far right and the other on the far left of the bar made for that use (do not pull/touch the fabric itself while pulling it).
The same way, once on the top, pull it down very very very gently, while checking that the fabric and the small peaces of plastic on the edges (which were out of their rails on the way up) are now in the rails.
Repeat this till it works fully.
Keep the blind down for 1-2 days for the fabric to get use to be at the proper place again.
Worked for me.
Ben, October 2009