Problem with os_dly_wait() and ULINK

Using ARTX Version 2.02 in our project we have the following problem:

We use the os_dly_wait()-function in two different tasks. Running our ULINK to debug the code and stepping through the source code we frequently get the following messages after the execution of this function:

Memory access not possible. CPU is in Idle, Sleep or Power-Down mode.

and

JTAG Communication Failure

I reduced the source code to the following lines:

void Task1 (void) _task_ TASK_1 {

unsigned long ulTest = 0;

        while(1){
                os_dly_wait (40);
                ulTest++;
        }
}

and

void Task2 (void) _task_ TASK_2 {

unsigned long ulTest = 0;

        while(1){
                os_dly_wait (40);
                ulTest++;
        }

the communication to the ULINK was interrupted, but the application on out target system is still running.

What can be the reason for this ??