Firefox 33 regression

Installing FF 33 from Rapps causes this:

(../../win32ss/user/ntuser/defwnd.c:1087) err: WM_SETREDRAW
(../../win32ss/user/ntuser/defwnd.c:1087) err: WM_SETREDRAW
(../../win32ss/user/ntuser/winpos.c:3046) err: NtUserSetWindowPos bad window handle!
(../../win32ss/user/ntuser/defwnd.c:1087) err: WM_SETREDRAW
(../../win32ss/user/ntuser/defwnd.c:1087) err: WM_SETREDRAW
(../../win32ss/user/ntuser/winpos.c:3046) err: NtUserSetWindowPos bad window handle!
(../../win32ss/user/ntuser/windc.c:749) err: [00020176] GetDC() without ReleaseDC()!
(../../win32ss/user/ntuser/windc.c:749) err: [00020176] GetDC() without ReleaseDC()!
(../../win32ss/user/ntuser/windc.c:749) err: [00020176] GetDC() without ReleaseDC()!
(../../lib/rtl/actctx.c:1395) Unsupported yet language attribute ((null))
(../../lib/rtl/actctx.c:2395) unknown element ms_asmv3:trustInfo
(../../lib/rtl/actctx.c:2395) unknown element ms_asmv3:application
(../../lib/rtl/actctx.c:2395) unknown element compatibility
WDMAUD.DRV - Thread detached
WDMAUD.DRV - Process detached
DRV_OPEN / DRV_CLOSE
DRV_ENABLE / DRV_DISABLE
DRV_FREE
Unfreed memory blocks: 0
(../../win32ss/user/ntuser/desktop.c:529) err: ptiLastInput is CLEARED!!
(../../dll/ntdll/ldr/ldrutils.c:1323) LDR: LdrpMapDll Relocating Image Name C:\Programme\Mozilla Firefox\sandboxbroker.dll (10000000 -> 002A0000)
(../../dll/ntdll/ldr/ldrutils.c:1362) Overlapping DLL: C:\Programme\Mozilla Firefox\mozglue.dll

Entered debugger on last-chance exception (Exception Code: 0xc0000005) (Page Fault)
Memory at 0x50414D52 could not be read: Page not present.
kdb:> bt
Eip:
<fastfat.sys:1d7b> drivers/filesystems/fastfat/close.c:61 (VfatCloseFile)
Frames:
<fastfat.sys:1e88> drivers/filesystems/fastfat/close.c:115 (VfatClose)
<fastfat.sys:d756> drivers/filesystems/fastfat/misc.c:119 (VfatDispatchRequest)
<fastfat.sys:dc2f> drivers/filesystems/fastfat/misc.c:181 (VfatBuildRequest)
<NTOSKRNL.EXE:7b183 (ntoskrnl/io/iomgr/irp.c:1207 (IofCallDriver))>
<NTOSKRNL.EXE:6d8d0 (ntoskrnl/io/iomgr/file.c:1015 (IopDeleteFile))>
<NTOSKRNL.EXE:109165 (ntoskrnl/ob/oblife.c:211 (ObpDeleteObject))>
<NTOSKRNL.EXE:10fce3 (ntoskrnl/ob/obref.c:237 (ObfDereferenceObject))>
<NTOSKRNL.EXE:1044c9 (ntoskrnl/ob/obhandle.c:752 (ObpCloseHandleTableEntry))>
<NTOSKRNL.EXE:105dfc (ntoskrnl/ob/obhandle.c:1745 (ObpCloseHandle))>
<NTOSKRNL.EXE:107d27 (ntoskrnl/ob/obhandle.c:3297 (NtClose))>
<NTOSKRNL.EXE:1423d5 (ntoskrnl/include/internal/arch/../i386/ke.h:689 (KiSystemServiceHandler))>
<NTOSKRNL.EXE:3d95 (:0 (KiFastCallEntry))>
<ntdll.dll:c7f1>
<KERNEL32.DLL:29b19>
<Firefox%20Setup%2033.0.exe:c417>
<Firefox%20Setup%2033.0.exe:c47e>
<Firefox%20Setup%2033.0.exe:c3ac>
<Firefox%20Setup%2033.0.exe:c9b8>
<Firefox%20Setup%2033.0.exe:117ee>
<Firefox%20Setup%2033.0.exe:11e6e>--- Press q to abort, any other key to continue —

A Revert of this rev made my 6 test installs die 2 times in between 1st stage and 2nd stage with a fatal VBox error, but the 4 others were nicely with FF.