Ok I see! I think the file is badly corrupted
You should use the recovery:
https://bitcointalk.org/index.php?topic=34028.msg2794856#msg2794856python pywallet.py --recover --recov_device c:\path\to\your\wallet.dat --recov_size 30Gio --recov_outputdir c:\recoveredwalelt
The rest should be obvious
Tell me if anything goes bad
If this doesn't recover the keys you wanted then I really think they're gone