Service Fails Unexpectedly with Access Violation in s1ppcass()

SYMPTOMS

   Application exception occurred:
   App: exe\snaservr.dbg (pid= <process ID>)
   Exception number: c0000005 (access violation)

[...]

function: s1ppcass
        01050c92 8b4924           mov     ecx,[ecx+0x24]
ds:0130ea06=????????
        01050c95 80491804         or      byte ptr [ecx+0x18],0x4
ds:0130ea06=??
        01050c99 8b14b5bcb00b01
ds:00000325=????????
                                  mov     edx,[s1rcb+0xe25c
(010bb0bc)+esi*4]
        01050ca0 33ff             xor     edi,edi
        01050ca2 894228           mov     [edx+0x28],eax
ds:02c70f82=????????
        01050ca5 eb4e             jmp     s1ppcass+0x1d5
(01050cf5)
        01050ca7 8b0cb5bcb00b01
ds:00000325=????????
                                  mov     ecx,[s1rcb+0xe25c
(010bb0bc)+esi*4]
        01050cae 33ff             xor     edi,edi
        01050cb0 57               push    edi
        01050cb1 8b4928           mov     ecx,[ecx+0x28]
ds:0130ea06=????????
FAULT ->01050cb4 8911             mov     [ecx],edx
ds:00000000=????????
        01050cb6 8b14b5bcb00b01
ds:00000325=????????
                                  mov     edx,[s1rcb+0xe25c
(010bb0bc)+esi*4]
        01050cbd 894228           mov     [edx+0x28],eax
ds:02c70f82=????????
        01050cc0 8b04b5bcb00b01
ds:00000325=????????
                                  mov     eax,[s1rcb+0xe25c
(010bb0bc)+esi*4]
        01050cc7 8b4c2414         mov     ecx,[esp+0x14]
ss:0249e913=????????
        01050ccb 8b4024           mov     eax,[eax+0x24]
ds:02c70f82=????????
        01050cce 8a5108           mov     dl,[ecx+0x8]
ds:0130ea06=??
        01050cd1 8a4808           mov     cl,[eax+0x8]
ds:02c70f82=??
        01050cd4 02ca             add     cl,dl
        01050cd6 8d542414         lea     edx,[esp+0x14]
ss:0249e913=????????
        01050cda 884808           mov     [eax+0x8],cl
ds:02c70f82=??
        01050cdd 8b442414         mov     eax,[esp+0x14]
ss:0249e913=????????

*----> Stack Back Trace <----*

 FramePtr ReturnAd Param#1  Param#2  Param#3  Param#4  Function
Name
 00000020 00000000 00000000 00000000 00000000 00000000
snaservr!s1ppcass
 (FPO: [EBP 0x00000000] [3,1,4])
 00000034 00000000 00000000 00000000 00000000 00000000
snaservr!<nosymbols>