if (X !is null && X.Y !is null) access crash

[Amex]

I don't understand why

if (X !is null && X.Y !is null) access crash

is crashing.

It is true that it is being used in a thread. It happens when I 
close down my app.

The whole point of the check is to make sure X is not null but it 
seems to be failing.

The debugger is showing X is not null yet X.Y is null. (Y is a 
delegate)

I believe this is because I'm not using shared(which causes 
problems with orange serdes) and the GC.

I'm not sure though.