RTX , Cortex-M4 and vector table

Hello,

When coding a simple project (Freescale K40 + Keil IDE) it's possible to set the vector table offset register to the correct ram address.
For example:
#define RAM_START (0x20000000 - ((RAM_SIZE * 1024)/2)) // SRAM is symmetrical around 0x20000000

After this setup, registering an interrupt is being done by setting its address in the correct offset (RAM_START_ADDRESS + 16 + IRQ number)
I've noticed that once the RTX kernel was added to the project, any attempt to modify the vector tables offset (SCB->VTOR = xx) caused the software to jump to hard abort.

Any help please :)

Thanks,
Eitan Michaelson.