In hind sight... you may want to set your autobackup to a couple of minutes... I just discovered a month or so back that With Windows XP, Autocad keeps a recent backup in:
"C:\Documents and Settings\kjam\Local Settings\Temp"
your location may be different, but you may be able to find a recent copy of your last file... I also don't know if the file is related to the autobackup setting or if this temporary file is automatically created with each change... The file has a name similar to:
05157S02_1_1_6334.sv$ (for drawing 05157S02.DWG)
I have AutoCAD lock up every so often with the message 'Missing Driver' and discovered this 'feature'. Unfortunately I found it a few days after losing half a day's work earlier on in the week.
Dik