In Notes 8.5.3 Standard on Mac 10.7.x (Lion), Notes client can hang with Spell Check. This occurs when "Spell Check before sending mail" is enabled and the dictionary is set to English - Canada.
Notes hangs when sending mail and running Spell Check
This has been identified as a product defect under SPR # JSTN8TFR4T.
Resolving the problem
This will not occur with the English - U.S. dictionary, or using the basic spell checker by adding:
to the Notes Preference file.