Server abending several times a month, middle of night. Suggestions?

Last abend log:

Server WHS_SERVER halted Wednesday, April 11, 2007 2:56:35.687 am
Abend 1 on P01: Server-5.60.05: Double Fault Processor Exception (Error
code 00000000)

Registers:
CS = 0008 DS = 0010 ES = 0010 FS = 0010 GS = 0010 SS = 0010
EAX = 00000311 EBX = 00010001 ECX = 00000000 EDX = 00000001
ESI = A015439B EDI = 00000000 EBP = 11111111 ESP = 00000003
EIP = 00224877 FLAGS = 00010002
00224877 E8B862FEFF CALL
SERVER.NLM|CallRegisteredPollingRoutines
EIP in SERVER.NLM at code start +00020517h

The violation occurred while processing the following instruction:
00224877 E8B862FEFF CALL SERVER.NLM|CallRegisteredPollingRoutines
0022487C EBA0 JMP 0022481E
0022487E E889F7FFFF CALL SERVER.NLM|kWorkToDoCheckAllRunFast
00224883 833D2001C0FB00 CMP [FBC00120]=00000000,00000000
0022488A 74E9 JZ 00224875
0022488C 833D3801C0FB00 CMP [FBC00138]=00000009,00000000
00224893 7EE0 JLE 00224875
00224895 A13C01C0FB MOV EAX,[FBC0013C]=8C906580
0022489A 85C0 TEST EAX,EAX
0022489C 7527 JNZ 002248C5



Running process: Processor 1: IDLE Thread Process
Thread Owned by NLM: SERVER.NLM
Stack pointer: C89A6FF8
OS Stack limit: C89A5040
CPU 1 (Thread C89A3480) is in a NO SLEEP state
Scheduling priority: 67371008
Wait state: 3031111 Intermedidate Goto READY
Stack:
Stack dump exceeded the valid memory limit

Additional Information:
The CPU encountered a problem executing code in SERVER.NLM. The
problem may be in that module or in data passed to that module by a
process owned by SERVER.NLM.

Loaded Modules:
TSANDS.NLM TSA for Novell eDirectory 7.x, 8.x
Version 10551.61 December 2, 2003
Code Address: 90665000h Length: 0001254Ch
Data Address: 853D9000h Length: 00001410h
CTSRVR.NLM CTSRVR
Version 3210.31 October 31, 1999
Code Address: 87F34000h Length: 00070145h
Data Address: 87E6B000h Length: 0002C570h
MONITOR.NLM NetWare Console Monitor
Version 12.01.09 May 5, 2004
Code Address: 87EB2000h Length: 00022AAFh
Data Address: 87ED6000h Length: 00005ED1h
TAPEALRT.NLM Tape Alert 2.1 SNMP Agent For NetWare (Build 614.000
09/02/03)
Version 9.01 September 2, 2003
Code Address: 89999000h Length: 0000A27Dh
Data Address: 899A5000h Length: 000021C0h
STANDARD.NLM BrightStor ARCserve 9.01 Standard Tape Support (Build
614.000 09/02/03)
Version 9.01 September 2, 2003
Code Address: 8987E000h Length: 0000E636h
Data Address: 8988E000h Length: 00098964h
UNIDMSVR.NLM CA Universal RPC Device Manager (Build 614.011 09/24/03)
Version 9.01 September 24, 2003
Code Address: 86F4D000h Length: 00023BCFh
Data Address: 86B63000h Length: 00004F06h
VALIDATE.NLM BrightStor ARCserve 9.01 ARCserve Validation Module
(Build 614.000 09/02/03)
Version 9.01 September 2, 2003
Code Address: 85C56000h Length: 000003CDh
Data Address: 85C58000h Length: 000001A0h
TAPESVR.NLM BrightStor ARCserve 9.01 SCSI Tape Driver (Build
614.000 09/02/03)
Version 9.01 September 2, 2003
Code Address: 8966A000h Length: 0007ED49h
Data Address: 896EB000h Length: 00047480h
DISCOVER.NLM CA Discovery Module (Build 614.007 09/16/03)
Version 9.01 September 16, 2003
Code Address: 8921B000h Length: 000129B8h