I just tried,
" As I stated earlier, if  I am  incorrect in this it is understandable for  I am  the student and you are the teacher. in WordPerfect and again received no error or warning messages from either the spell checker or the Grammatik. I think jheem's suggestion is one that bears investigating. Check the language settings for your WordPerfect, to make sure that the correct dictionaries and grammar tools are being used. I would also recommend checking in at 
http://www.wpuniverse.com, a help forum for users of WordPerfect, in case there is a glitch in your copy. Clearly, there is nothing wrong with the sentence as you have posted it here.