ya as you have described the possible solution i have tried them all.even i am using those hex files that come from pjrc site.
but its not working and when i run c command it run successfuly but when i try to see through the edit command the memory it shows the previous garbage values in it no 0's are shown in ram.
it means it never clears the memory.
but flash erase zumper and z command from menu is also not working.
what should i do now i have purchased the board from pjrc some 2 weeks ago and this board has given me nightmares,not a single program has run in that uptill now.
please suggest me somthing waiting for ur reply.