WPA-PSK Encryption Key

Hi everybody!
I'm new here and I got a problem with changing my WPA-PSK Encryption Key or WIFI password for my Thomson TG585v7 router.
I do the following:
- Home > Home Network > Interfaces > WLAN: ThomsonBFB0C9 and then I got this picture:
Attachment 236758
Now, I always refresh that page when I change my password, (and my router restart by its own),and after few seconds in the box for WPA-PSK Encryption Key is AGAIN my old password.
Please, if anybody can help let me know.
PS- Sorry for my bad English.

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