Let me elaborate a little bit on how the editor dropdown buttons works - the editor's dropdown buttons (in this case the Ajax Spellchecker) are designed to work with already selected value. But, when you use the dropdown button for the first time you should first select the value to be applied (the Language). The next time you click on the dropdown button it will automatically use the previously selected value. If you want to change the value, just use the little arrow. However, in the ASP.NET version of RadEditor for MOSS (4.x), when spellchecking in different languages, you need to always select the spellchecking language, before spellchecking. This issue is fixed in the new ASP.NET AJAX version of RadEditor for MOSS (5.x) and once you select a language it will be automatically used.
For convenience, I attached a sample video that demonstrates how the editor's dropdown buttons works.
the Telerik team
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