[ODE] Crash when calling dJointCreateContact in release version

[Daniel Punch]

Hey all,

I've had a weird bug on and off, sometimes my game crashes and sometimes 
it doesn't. At the moment it is only manifesting in the release build of 
the game.

The program crashes on the line:
dJointID c = dJointCreateContact (world,contactgroup,&contact[i]);

With the error:
Unhandled exception at 0x10034a43 in C2T.exe: 0xC0000005: Access 
violation writing location 0x00000000.

I've had this bug before (on the PS2 and on the PC) but it sometimes 
seems to remedy itself, seemingly at random (never a good sign... 
possibly memory leaks?).

I also, very occasionally, get a crash from the heightfield:
dIASSERT( ( dx + dEpsilon >= 0.0f ) && ( dx - dEpsilon <= 1.0f ) );

Any suggestions?

Thanks for your time,
Daniel Punch