All changes lost though clicking save w/ Access Violation

Excel 2000 with SP3. User will be working on the file all day long clicking save but not closing Excel. This is a large file with 37,000+ cells and some very complicated formulas. Takes a lot of time to do so the user clicks Save frequently. After about 7 hours of working on this file she receives a new email notification from Outlook 2k. She clicks Yes to read it, it opens the email, she clicks the reply button and BOOM! Application Error has occured and a Dr. Watson is created. She then, without rebooting, opens the file to continue working and all 7 hours of work are gone. None of the saves actually took. Our Win2k server undelete program shows nothing deleted and the file modification time stamp has the same time as the Dr. Watson time stamp. I searched all over to make sure she wasn't truely saving somewhere else. This did not come from an email attachment. It was saved on our server the day prior and opened up from there. The Dr. Watson is showing:
Application exception occurred:
App: (pid=1500)
When: 6/8/2004 @ 15:10:59.260
Exception number: c0000005 (access violation)

*----> System Information <----*
Computer Name: compname
User Name: sgonzale
Number of Processors: 1
Processor Type: x86 Family 15 Model 2 Stepping 7
Windows 2000 Version: 5.0
Current Build: 2195
Service Pack: 3
Current Type: Uniprocessor Free
Registered Organization: Lockton Companies
Registered Owner: Susan Gonzales

*----> Task List <----*
0 Idle.exe
8 System.exe
152 SMSS.exe
176 CSRSS.exe
196 WINLOGON.exe
224 SERVICES.exe
236 LSASS.exe
424 svchost.exe
448 spoolsv.exe
528 svchost.exe
592 ntrtscan.exe
620 regsvc.exe
656 mstask.exe
676 tmlisten.exe
760 WinMgmt.exe
776 WinVNC.exe
800 MsPMSPSv.exe
816 svchost.exe
220 OfcDog.exe
1104 explorer.exe
1212 PccNTMon.exe
1272 hkcmd.exe
1016 ExCnvt.exe
1324 astray.exe
1084 igfxtray.exe
1340 acrotray.exe
1360 hpnsjtr.exe
1296 OUTLOOK.exe
1392 MAPISP32.exe
1416 svchost.exe
1500 EXCEL.exe
1256 wmplayer.exe
1728 DRWTSN32.exe
0 _Total.exe