Hi
I don't think they spoiled something working properly. However some things changed, so some things may appear, although not showing up earlier.
My first bet is running out of stack. Stack requirements for functions may change from one OS to another, and I guess the newer OS, the higher requirement...
The second choice would be calling function from Task (even not directly), where you must have complete Process structure.
There are some tools that can help you - most obviously with stack, but this looks like heavy tracing job for you.
Good luck
