I've just defused this popup which happened every time my wife logged on to our iMac with her account - but not when I did with mine.
I logged with my wife's credentials and examined her login items (System Preferences/Users & Groups/Login Items) - but there was nothing suspicious there. Just the regular 'iTunes Helper' thing.
Next I examined her Launch Agents (From the finder menu select Go, hold down the Alt key until the Library option appears, select library, Launch Agents)
I examined each non-apple plist file there with TextEdit (there were only a couple). The offending item was the Facebook Video Chat demon - with various references to Java in the PList. She doesn't use Facebook video chat - so I simply deleted the plist file.
Voila - no more popups when she logs in.
Other places to check are /Library/LaunchAgents, /Library/LaunchDemons, /System/Library/LaunchAgents & /System/Library/LaunchDemons - but be really careful before deleting anything there. Examine the Plist & make sure you understand what it's launching. And in particular don't delete anything beginning with 'com.apple', or 'org.'