Debugging an access violation

I'm using a large closed-source framework. I recently added a new entity, and now I'm getting access violations when performing some actions. However, they occur on calls from within the framework, so I don't know what I've implemented wrong, since I don't get a call stack.

The violation is reported in the function _CRTIMP PFLS_GETVALUE_FUNCTION __cdecl __set_flsgetvalue() defined in the CRT file tidtable.c. The specific row is PFLS_GETVALUE_FUNCTION flsGetValue = FLS_GETVALUE;. I'm not sure, but I think it is related to function pointers?

The error message is Unhandled exception at 0x0000007a in fmwk.exe: 0xC0000005: Access violation reading location 0x0000007a.. My interpretation is that it's attempting to access something at offset 0x7a into an object, but it's acually given a null pointer. Is this correct? If it is, is there a way of finding what that offset corresponds to?

Below is the call stack:

0000007a()  
fmwk.dll!100f2630()     
[Frames below may be incorrect and/or missing, no symbols loaded for fmwk.dll]  

<lots of framework and windows dlls>

fmwk.exe!00402ef4()     
msvcr100.dll!__set_flsgetvalue()  Line 145 + 0xc bytes  C
msvcr100.dll!_getptd_noexit()  Line 498 + 0x7 bytes C
msvcr100.dll!_getptd()  Line 523 + 0x5 bytes    C
msvcr100.dll!_LocaleUpdate::_LocaleUpdate(localeinfo_struct * plocinfo=0x00000000)  Line 243 + 0x5 bytes    C++
msvcr100.dll!x_ismbbtype_l(localeinfo_struct * plocinfo=0x00000000, unsigned int tst=0, int cmask=1386664, int kmask=1414714)  Line 219 C++
msvcr100.dll!_ismbblead(unsigned int tst=0)  Line 172 + 0xe bytes   C++
fmwk.exe!004010a0()     
fmwk.exe!00404d61()     
kernel32.dll!7c817077()     

Use Application Verifier to debug this access violation. It should stop execution earlier when bad thing happens with better call stack than this one.

Looks like you dereferenced NULL pointer somewhere but program did not crash immediately since it is Undefined Behaviour, continued executing and crashed a bit later with weird call stack.