Same problem here (with firefox AND safari and chrome),

editor links set to relative,

 

containing page : ="/Admin/Pages.aspx?pageID=121"

 

If i set a link to an anchor tag,

 

in firefox & co, the editor takes the containing page in the url: <a href="http://cutesoft.net/Admin/Pages.aspx?pageID=121#a1"></a>

while working ok in internet explorer : <a href="#a1">

 

simply opening the page with IE recovers all links in the editor to the correct relative hre,

while opening in other browsers trash the links...

 

internet explorer 8

firefox 3.0.18