no device found !!

Dear sir,
I am using xbee pro s1 with xbee shield now some problem appear when i have connected xbee for the first time.Firstly the system was showing, “there is not an active bootloader in the module”. Later when i tried to update my xbee device,the system was showing, " could not read the hardware version of the radio module." Then i found some bypass system and that worked i successfully configured them. After sometime when i try to reconnect xbee with PC it shows “no device found”.
I Can’t work with the device and troubleshoot any problem regarding this…I have taken every single help provided in the community sites…
Sir,I Expect your kind attention and your help to solve the this issue… Now i am stuck in the middle of my final project.

I would suggest you send an email to explaining exactly what hardware you have (Full part numbers) and firmware versions along with the exact error messages.