Overlay problem with interrupt (with NOOL set)

I have a overlay problem:
I've got one function who is called from main and from my interrupt service routine.
When the interrupt calls the function my local variables point to an indefinite adress. I have the problem however I deactivate overlaing.
My programm:

void main (void)
{
...
eventChannelPtr = XSDevice_GetEventChanByID( &XSIM_DeviceGroups, groupID, chanID)}
}

void task_1ms(void) interrupt 1	using 1
{
...
eventChannelPtr = XSDevice_GetEventChanByID( &XSIM_DeviceGroups, groupID, chanID);
}

tXSEvent_ChannelPtr XSDevice_GetEventChanByID( tXSDevice_DeviceEntry* deviceEntryPtr, tXS_Group groupID, tXS_Channel chanID)
{
  tXSEvent_SourcePtr eventSrcEntry;
  tXSEvent_ChannelPtr retVal;
  ...
  eventSrcEntry = &deviceEntryPtr->eventListPtr[groupID];
}