Firefox 4 quits unexpectedly running Cucumber/Capybara/Webdriver

I just updated to the latest Firefox (4) and now our Cucumber, Capybara and Webdriver test suite is throwing errors when it tries to launch Firefox (anything marked with @javascript).

Our test suite was running fine (and fully passing) before I upgraded to Firefox 4 yesterday.

Here are the problem details as would be reported to Apple (I'm on a Mac):

Process:         firefox-bin [756]
Path:            /Applications/Firefox.app/Contents/MacOS/firefox-bin
Identifier:      firefox-bin
Version:         ??? (???)
Code Type:       X86-64 (Native)
Parent Process:  ruby [656]

Interval Since Last Report:          74 sec
Crashes Since Last Report:           5
Per-App Interval Since Last Report:  0 sec
Per-App Crashes Since Last Report:   5

Date/Time:       2011-03-23 07:52:28.298 -0700
OS Version:      Mac OS X 10.5.8 (9L31a)
Report Version:  6
Anonymous UUID:  8DC774A8-BD92-4645-8720-2D39B03B36AF

Exception Type:  EXC_BREAKPOINT (SIGTRAP)
Exception Codes: 0x0000000000000002, 0x0000000000000000
Crashed Thread:  0

Dyld Error Message:
  unknown required load command 0x80000022

I haven't been able to find any other reference of this issue online and don't know where to start with t开发者_StackOverflowroubleshooting it...

Any help is greatly appreciated. Thanks.

Update: after going back to 3.6 things work again. It seems the problem is specifically with Firefox 4 (both via update and directly from the site).

This is an issue with Firefox when launched from the command line on 10.5. It has been reported to Mozilla, but closed as WONTFIX.

Obviously not the ideal solution, but you can work around this by stripping the x86_64 parts of the firefox-bin binary:

cd /Applications/Firefox.app/Contents/MacOS
mv firefox-bin firefox-bin.original
ditto --arch i386 firefox-bin.original firefox-bin