REGRESSION: Firefox 2.0.0.20 crashes at launch or becomes unresponsive

Official 47656.
Fresh ros installation, install FF, launch it, it doesn't show any page or shows it partially then stops loading. If you close it and reopen it, it crashes, same thing if you restart ros.
First time after closing it and reopening it:
Entered debugger on first-chance exception (Exception Code: 0xc0000005) (Page Fault)
Memory at 0x00000006 could not be written: Page not present.
kdb:> bt
Eip:
<0290a627>
Frames:
<04778b0c>
Couldn't access memory at 0x247C8B5B!
kdb:>

another backtrace:
Entered debugger on first-chance exception (Exception Code: 0xc0000005) (Page Fault)
Memory at 0x352E3081 could not be read: Page not present.
kdb:> bt
Eip:
<js3250.dll:1faaa>
Frames:
<js3250.dll:1fb15>
<js3250.dll:1fb15>
<js3250.dll:1fb15>
<js3250.dll:1fb15>
<js3250.dll:1fb15>
<js3250.dll:1fb15>
<js3250.dll:1fb15>
<js3250.dll:1fb15>
<js3250.dll:1f9f4>
<js3250.dll:1fb15>
<js3250.dll:1f9f4>
<js3250.dll:2017f>
<js3250.dll:2a0e>
<firefox.exe:4563c7>
<firefox.exe:100d>
<kernel32.dll:2f747>
<00000000>
kdb:>