This error usually indicates a corrupt dictionary file. Please check your spell dictionaries (*.tdf files) and make sure that they are the same as the originals from the RadEditor installation. If you have tried to make modifications to some of the tdf dictionary files, you can tell us what you wanted to change and we will tell you how to do it.
The words in the spell dictionary are ordered by length. The error details mean that there was a word of "length 7" or more somewhere in the "length 7" words part of the dictionary.
the Telerik team
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