Editing posts w/quotation marks

I use quotation marks frequently, and have noticed that whenever I try to go back and edit a post with quotation marks, I can only edit it once, before encountering an error message telling me to contact an administrator, or worse, often it won't even let me edit it once. Also, wherever the quotation marks began, the text afterward is erased, so it's necessary to copy + paste the post before editing to save the remaining text.