C6747 program local value to 0！

my platform is CCS3.3, C6747, bios v5.41, code generation v6.11.
    my program like this:
 Uart_TSK1()
 {
  while(1)
  {
   SemPend（event1）;
   uartDeal(1);
  }
 }
 .........
 Uart_TSK5()
 {
  while(1)
  {
   SemPend（event5）;
   uartDeal(5);
  }
 }

 while uartDeal like this:
 void uartDeal(int port)
 {
       ....
       char sendBuf[64] = {0};
       int uartFifo[2] = {16,64};
  
              .....
 }

 Today, I find thar the value of uartFifo[2] is {0, 0} when debuging a section of program,
   and then I think any stack of Uart_TSK1~Uart_TSK5 is Overflow, when the DSP/BIOS kenerl tell
   me all the TSK stack is normal, so I do not understand the question.
        while a second question, there is a Common sense debug with CCS, if the memory become red,
   it means the domain of the memory had been changed, but if some memory become light blue,what
   does it means to me?
       thanks
       --thomas