No. The SW Uart is working as follows: First it sends a string to the pc (i.e. 'WAIT') and then it waits for 250 ms. for the replay. If PC does not responds then it disables the IT0, i.e. it disables the recieve operation. And it does this every 5 seconds. If pc responds in 250 ms. then it takes the whole packet from the pc and again disables the IT0.
The problem occures when it is connected to the pc, but not communicate with pc. And nearly 1 or 2 hours later after i connect it to Pc. So, i think there cannot be any problem in software, such as stack overflow.
Regards.
Ertan Balaban.