Firefox 3b5 "engine has no file" fater dist-upgrade

[Steph]

Hello,

Few minutes ago, after a aptitude dist-upgrade, firefox is KO and
displays this error :

ASSERT: *** Search: _installLocation: engine has no file!
Stack Trace:
0:ENSURE_WARN(false,_installLocation: engine has no file!,2147500037)
1:()
2:()
3:()
4:epsGetAttr([object Object],hidden)
5:()
6:()
7:currentEngine()
8:get_currentEngine()
9:updateDisplay()
10:init()
11:([object XULElement],6)


I've ran aptitude install on any XUL component I found interesting, or
on any language pack, but nothing works.

Any idea to solve this ?

Thanks