Thanks for your reply. I am using HTTP protocol. Actually my file(XLS) is successfully downloaded as an attachment, i can open it,view it . I am using Commons package for parsing it, and is gives exception while parsing.
Actually, after downloading the file , i was using jxl package to get(read) the cell contents, but i used table format to write it on output...so when i tried to upload it again, it was not pure xls file, hence the biff exception.