If the infuser is actually at the bottom you should be able to release it by using the two red tabs.
If infuser is not at the bottom you should be able to get the tray back in.
If all else fails. Unplug the machine. Remove the machine casing and carry out a manual wind of the rack. When you take the casing off you will see a long threaded shaft rack. Remove the drive motor (4 screws hold this in place) Turn the rack screw by hand to wind the infuser up/down until you can get the tray back in. Refit the motor. Power back on and test
Garry Knox, August 2013
Same thing has happened to mine this morning. Door flew open and now will not catch closed. Cannot remove diffused, drip tray or grounds box. Cannot switch on. Quoted £50 transport and labour before parts and repair. Does anybody have answer for DIY repair.
Mike, June 2013
Exact same thing just happened to mine... the diffuser dropped to the bottom and is dead stuck in place and cannot remove it... I loved this machine... Years of great, constant and consistent service...