I’ve been using FlexBuiler 3 on my MacBookPro now for about 2 weeks and have been increasingly frustrated with the performance of Flex Builder when in debug mode (when using Firefox). I figured it must be related to JVM settings, etc. Finally, I decided to goolge my woes and stumbled upon the post below indicating the the Cool Iris Preview plug-in for firefox was to blame. I promptly uninstalled the plugin an viola’ – fast debugging once again!
Kudos to Vic @ Vic on Flex for finding this solution!