Thanks for your report Vincenzo. After some investigation we found
that this was caused by some Firefox feature which auto completes
forms when you "go back" to them. We were able to fix it with the help
of some Javascript hack. We recognize this is not a portable solution
(other browsers may behave differently) and this JS hack is not cross-
browser, but we still think it's worth introducing it since the
problem you mentioned imposes a somewhat important privacy concern. So
this was fixed by introducing a hack that "blocks" this feature from
Firefox 3, but others browsers may still suffer from this very subtle
"bug". However browsers consider this a feature, not a bug :).
We're still investigating how to block this feature in other browsers.
Pablo.