Perhaps this will assist you in updating PWM for FF3: Using Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.9b3pre) Gecko/2007121305 Minefield/3.0b3pre - Build ID: 2007121305 and other recent nightly releases, PWM 1.7 works partially. I installed PWM and copied the passwordmaker.rdf file from my FF profile for FF 2.x into my profile for FF3.
Existing entries in PWM (from FF 2.x) work in the FF nightlies, so that when I go to a site that has a password setup in PWM, PWM properly enters the relevant information and I can log on.
However, if I look at PWM itself, all (yes, all) of the boxes for entering information are empty. So, if I want to see that the password, URL, etc., are for sites where PWM is working with FF3 nightly releases, I see nothing at all.