Most if the links that appear on the menu navigation are
generated from the file called "CORE.CSS". In the file there are a couple of
methods that render this menu item. You could simply override this in this
page and rebuild the link. Obviously you shouldn't modify the main file, you
might want to copy the original as a backup. The other option would be to
add a Content Editor Web Part to the page you are suing and write the
override JavaScript there. Both would work.

I think we may be talking about different things. The links on the
navigation menus such as the Quick Launch and Top link  Bar work
fine. The link that is generated from the document  edit menu when
you wan to email  someone a link to the document doesn't work.

I was talking about the right thing but wrote
navigation for some reason!! No idea why!! J The way to do it still stands
though, I wrote a blog post a while ago about modifying the List Item menu
items. Check it out here:

www.sharepointblogs.com/.../18676.aspx

www.sharepointblogs.com/.../19500.aspx

Both of these posts talk about adding new menu items but the principle is
still the same for modifying existing ones.

Do you happen to know what part of the
Core.js file drives the generation of the document  URL? If you
happen to know where to start and don't mind sharing that reference,
it would be great as our developers will have to hunt for it
otherwise.

It can be found in the function called "AddSendSubMenu".
Search for the string variable called "L_SendToEmail_Text". Once you find
this, this is the section that is used to render the link. The actual email
link is generated by concatenating a few other variables together into a
variable called "fileURL". This is all then pushed into a JavaScript
function called "navigateEmailToLink". The JavaScript collects values from
the "ItemTable", mainly the Server URL then substrings part of it and
concatenates it to the "currentItemUrl" along with a few extras.

It can be found in the function called "AddSendSubMenu".
Search for the string variable called "L_SendToEmail_Text". Once you find
this, this is the section that is used to render the link. The actual email
link is generated by concatenating a few other variables together into a
variable called "fileURL". This is all then pushed into a JavaScript
function called "navigateEmailToLink". The JavaScript collects values from
the "ItemTable", mainly the Server URL then substrings part of it and
concatenates it to the "currentItemUrl" along with a few extras.

It can be found in the function called "AddSendSubMenu".
Search for the string variable called "L_SendToEmail_Text". Once you find
this, this is the section that is used to render the link. The actual email
link is generated by concatenating a few other variables together into a
variable called "fileURL". This is all then pushed into a JavaScript
function called "navigateEmailToLink". The JavaScript collects values from
the "ItemTable", mainly the Server URL then substrings part of it and
concatenates it to the "currentItemUrl" along with a few extras.