'Value Object' and 'Immutable Object' are a contradiction in terms. Immutability refers to values, not 'objects'.
Immutable is just a word that means unchanging, as in "immutable laws of nature". . Consequently Objects can be immutable if they cannot change after creation. This seems a pretty commonly held view http://en.wikipedia.org/wiki/Immutable_object
How would you define Objects and Values?
More to the point, an object has agency: It gets to decide how to interpret messages sent to it (this is why we say that putting setters on classes turns objects back into mere data structures [1]).
http://www.devx.com/enterprise/the-vision-of-kay-and-fieldin... (right after the seventh paragraph)
https://www.google.com/search?as_q=MacLennan+Values+and+Obje...
These are orthogonal ideas; not contradictory ones.