The stop/Dequeue process is not working for me in safari (as in absolutely nothing happens), I noticed this with Start Backup option as well. However, BackupPC began backing the host up after I restarted BackupPC.

BackupPC version: 3.0
OS of Browser that showed bug: OSX 10.5, Safari 3.0

-) I did a quick check of the usual suspects such as apache logs, backuppc logs and didn't see any references. 

-) I checked the url strings in the browsers and got this in safari:

BackupPC_Admin?host=localhost&action=

(page remained on the localhost default page)

And this in FireFox:

http://airto.hosted.ats.ucla.edu:8080/cgi-bin/BackupPC_Admin?host=localhost&action=Stop_Dequeue_Backup

So it seems a string/option is being dropped somewhere. 

I'll dig deeper after setting up backuppc for my clients via firefox.

James A. Kyle
UCLA Brain Mapping Center
AIM: krunk337