I had the same thing happen.  Like you suggested above, it looked like it happend during an IP scan. 
I also have my Lansweeper running in a VM using ESXi v4. 
Lansweeper Log3/30/2010 12:11:44 AM: Attempted to read or write protected memory. This is often an indication that other memory is corrupt.
System Information
Host Name:                 XXX
OS Name:                   Microsoft(R) Windows(R) Server 2003, Standard Edition
OS Version:                5.2.3790 Service Pack 2 Build 3790
OS Manufacturer:           Microsoft Corporation
OS Configuration:          Member Server
OS Build Type:             Uniprocessor Free
Registered Owner:          xxx
Registered Organization:   xxx
Product ID:                xxx
Original Install Date:     1/9/2009, 4:10:01 PM
System Up Time:            17 Days, 18 Hours, 23 Minutes, 27 Seconds
System Manufacturer:       VMware, Inc.
System Model:              VMware Virtual Platform
System Type:               X86-based PC
Processor(s):              1 Processor(s) Installed.
                           [01]: x86 Family 6 Model 26 Stepping 5 GenuineIntel ~2667 Mhz
BIOS Version:              INTEL  - 6040000
Windows Directory:         C:\WINDOWS
System Directory:          C:\WINDOWS\system32
Boot Device:               \Device\HarddiskVolume1
System Locale:             en-us;English (United States)
Input Locale:              en-us;English (United States)
Time Zone:                 (GMT-05:00) Eastern Time (US & Canada)
Total Physical Memory:     1,023 MB
Available Physical Memory: 426 MB
Page File: Max Size:       1,318 MB
Page File: Available:      759 MB
Page File: In Use:         559 MB
Page File Location(s):     C:\pagefile.sys
Domain:                    xxx
Logon Server:              \\xxx
Event Viewer: System
Event Type:	Error
Event Source:	Service Control Manager
Event Category:	None
Event ID:	7034
Date:		3/30/2010
Time:		12:12:43 AM
User:		N/A
Computer:	xxx
Description:
The Lansweeper Server service terminated unexpectedly.  It has done this 1 time(s).
For more information, see Help and Support Center at http://go.microsoft.com/fwlink/events.asp.
Event Viewer: ApplicationEvent Type:	Error
Event Source:	.NET Runtime 2.0 Error Reporting
Event Category:	None
Event ID:	1000
Date:		3/30/2010
Time:		12:12:08 AM
User:		N/A
Computer:	xxx
Description:
Faulting application lansweeperservice.exe, version 4.0.0.11, stamp 4b99f67b, faulting module msvcr80.dll, version 8.0.50727.3053, stamp 4889d619, debug? 0, fault address 0x000150d8.
For more information, see Help and Support Center at http://go.microsoft.com/fwlink/events.asp.
Data:
0000: 41 00 70 00 70 00 6c 00   A.p.p.l.
0008: 69 00 63 00 61 00 74 00   i.c.a.t.
0010: 69 00 6f 00 6e 00 20 00   i.o.n. .
0018: 46 00 61 00 69 00 6c 00   F.a.i.l.
0020: 75 00 72 00 65 00 20 00   u.r.e. .
0028: 20 00 6c 00 61 00 6e 00    .l.a.n.
0030: 73 00 77 00 65 00 65 00   s.w.e.e.
0038: 70 00 65 00 72 00 73 00   p.e.r.s.
0040: 65 00 72 00 76 00 69 00   e.r.v.i.
0048: 63 00 65 00 2e 00 65 00   c.e...e.
0050: 78 00 65 00 20 00 34 00   x.e. .4.
0058: 2e 00 30 00 2e 00 30 00   ..0...0.
0060: 2e 00 31 00 31 00 20 00   ..1.1. .
0068: 34 00 62 00 39 00 39 00   4.b.9.9.
0070: 66 00 36 00 37 00 62 00   f.6.7.b.
0078: 20 00 69 00 6e 00 20 00    .i.n. .
0080: 6d 00 73 00 76 00 63 00   m.s.v.c.
0088: 72 00 38 00 30 00 2e 00   r.8.0...
0090: 64 00 6c 00 6c 00 20 00   d.l.l. .
0098: 38 00 2e 00 30 00 2e 00   8...0...
00a0: 35 00 30 00 37 00 32 00   5.0.7.2.
00a8: 37 00 2e 00 33 00 30 00   7...3.0.
00b0: 35 00 33 00 20 00 34 00   5.3. .4.
00b8: 38 00 38 00 39 00 64 00   8.8.9.d.
00c0: 36 00 31 00 39 00 20 00   6.1.9. .
00c8: 66 00 44 00 65 00 62 00   f.D.e.b.
00d0: 75 00 67 00 20 00 30 00   u.g. .0.
00d8: 20 00 61 00 74 00 20 00    .a.t. .
00e0: 6f 00 66 00 66 00 73 00   o.f.f.s.
00e8: 65 00 74 00 20 00 30 00   e.t. .0.
00f0: 30 00 30 00 31 00 35 00   0.0.1.5.
00f8: 30 00 64 00 38 00 0d 00   0.d.8...
0100: 0a 00                     ..