MCDU Stuck at final approach

[lwc.711022 3]

Hi all, 

I just flow from EGPH to EGLL the week before on IVAO's event.

When I was in final approach and holding at LAM, the ATC told me to swap to Runway 27R instead of Runway 27L for my arrival.

But as I was going to change the Arrival Runway and enter the initial approach fix into my MCDU, the whole thing stuck, just like the one in the photos.

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I can do nothing on the MCDU since it stuck at that page and I cannot activate the Approach. It still stuck at DES mode after I touched down and shut down my engine.

I still not able to figure it out what was happening.

Do anyone have any solution or idea of what was going on?

I am using the FSX version.