Hi Paola,
I don't know if something it's changed in last firmwares, but since the keyboard is actually embedded with the dictionary with a source file that contains two keyboards, one for the 602/902 series and one for the 603/903 separated by a blank line, my guess is that the firmware you're using is encountering some error when checking for the last keyboard, providing you the first keyboard type.
If the Webster's is one of those downloaded from the pocketbook dictionary thread, maybe there is need of a newer dictionary converter to get rid of the problem...
Or maybe I'm wrong.

I'd be glad to try your file with my old 2.0.5 firmware if you'll provide me a download link.