I am sometimes able to receive the data successfully where as sometimes i am not able to receive it at all.

I am not able to solve the problem nor have clue to this !

With the info given only wild guesses are possible so here is some questions
1) are you one of those that believe that RS232 is possible without a MAX232 (equivalent)
2) is your serial routine interrupt driven?
3) if yes to the above, do you have interrupts at a higher priority?
4) if 1) is yes or 2 is no - fix your hardware/code, otherwise post your code (remember pre and /pre)

Erik