My mod crashes: exception code 0xc0000005

[ViterboKnight]

I'm not sure if this is the right forum to post it.

This is the exception I'm having with my mod. (note: my mod has an edited DLL).

I'm playing a moment when a new civilization enters the game (like when you create a colony). I have two savegames: the savegame A is just before the new civilization appears, the savegame B is just after the new civilization is entered.
If I load A, exit the game, reenter, and load B, no problem.
If I load B, exit the game, reenter, and load A, no problem.
If I load B and then load A without exiting the game, it crashes.
In the xml.log, I can't find anything useful. However, in the Windows EventViewer, there's an entry saying:

Faulting application Civ4BeyondSword.exe, version 3.1.9.0, time stamp 0x4a0c27e6, faulting module CvGameCoreDLL.dll, version 0.0.0.0, time stamp 0x4ad4e257, exception code 0xc0000005, fault offset 0x00256130, process id 0x11ac, application start time 0x01ca4f290ae2a740.

Is it a somehow known problem?
Can anyone tell me what to check or to try? Or any hint?

My system:
Windows Vista Ultimate SP1
Inter core duo T6400, 4Gb ram
Video adapter: Radeon HD4530