With the message
Error: Passwords do not match, please retype. Cacti tried to make my life horrible today, but not with me.
If you are running Cacti 0.8.7b (which is the standard version located in the Ubuntu repositories) you will be prompted with this error after editing a host using Firefox 3. The error is based on an auto complete bug within the form. There are two solutions to avoid the problem (which worked for me):
The easiest way to apply this patch is to cd to your cacti directory and:
curl -L http://forums.cacti.net/download.php?id=14681
curl -L http://forums.cacti.net/download.php?id=14681|patch -p1 -N