The problem is that if you use nvarchar(MAX), you may not be able to manipulate the string in BO, so that makes it hard to manipulate it. You could try to do something like this in a formula:
replace({table.long field}, ';', chr(13) + chr(10))
This will replace each of the semi-colons with a carriage return/line feed. You'd then put that formula on your report, make it as wide as you need to and turn on Can Grow. You'd get your new lines where you want them that way. However, unless you have a very small, well-trusted set of users, they're not always going to do what you ask them to!
Also, Crystal WILL read carriage return in long text. So, you could have the users just press the Enter key instead of a semi-colon. It would be more natural and easier for them to remember.
If the data absolutely needs to be formatted a specific way, regardless of how the users enter it, you need to find some other way to set up the data entry to ensure that it's formatted correctly.
-Dell