Can you please try to use another dictionary for example fr-FR.tdf (delete the English one) and set the SpellCheckProvider
to EditDistance, e.g.
<telerik:RadSpell SpellCheckProvider="EditDistanceProvider" Language="fr-FR"
Does the problem still exist?
This is the only thread that I found with this error: http://www.telerik.com/community/forums/aspnet-ajax/spell/spell-check-server-error-500.aspx
the Telerik team
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