Unknown Crash and CFR register is not update

Hi,
i have a strange problem with STR7:
everytime it crashes for unknown reason.
Now i will explain better:
my microcontroller has watchdog enabled and it has a voltage supervisor.
I use EMI:
bank 0 an external flash(15 waitstate),
bank 1 a cpld(3 waitstate),
bank 2 an external adc converter(3 waitstate)

I use 3 serial port at 230400 and 1 at 115200;

number of tasks (17) and number of timer (4) correctly declared;
heap size 0x100;
supervisor mode 0x20
interrupt mode 0x40
system mode 0x50

Sometimes some os_tmr start; only one os_tmr every 1 minute is recalled with os_tmr_create
(now i will try to delete this timer).

It seems that no voltage supervisor reset micro (saw it with oscilloscope)
It seems that no watchdog reset micro (saw it into CFR resgister)
It seems a micro crash but i don't know why.
It seems also that if i have done a micro reset by watchdog and after micro reset for my unknown crash, into CFR register i read a watchdog reset; how is possible (CFR resgister is not update)???

Using 4 serial ports at this speed some problem with:

void __swi(8) os_lock (void);
void __SWI_8 (void) { /* This function must be executed from supervisor mode protected from */ /* interrupts. STR71x interrupts are disabled with a delay because EIC */ /* pheripheral may run with a slower clock than CPU. */ OS_LOCK(); /* Wait for 'OS_LOCK' to become active. */ __nop(); __nop(); __nop();
}

In the previous versions of mdk you must increase __nop to work properly interrupt
but problem must be solved.

Any idea??? Please help me!!

PS: I use the last mdk_arm and last version of library and no overflow occurs!!