jar utility in 1.1.x and 1.2x does not adhere to manifest file format specification when the name/value pair exceeds 72 characters.
The speicfication states that lines in the manifest which exceed 72 bytes should be split over multiple lines using space as a continuation character on the next line.

The manifest is created by share/sun/sun/tools/jar/Manifest.java which uses the MessageHeader class share/sun/sun/net/www/MessageHeader.java. MessageHeader implements the RFC822 MIME header message format but does not handle line continuation.

Specification details available at :-
http://java.sun.com/products/jdk/1.1/docs/guide/jar/manifest.html
See sections "3. Name-value pair and sections" and "7. Note".