Please save my driver locked by BITLOCKER

Dear all,
please show me any answer for this problem, it relating to BITLOCKER (Win 7).

- I have an external driver (300GB) and it is locked by BitLocker. I set automatic log into my computer so when i used Acronis yesterday to split the driver to two parts, i did not remember that i had not removed Bitlocker from it.
- The result is, just after when i start splitting, Acronis noticed that occurred an error. I wondered and come back to open the driver. Unfortunately, i cannot open it because of an error. I think it relating to Recovery Key of BitLocker. I captured the error notice as below pic.

Any body please help me? Thank you very much! I really want to join my driver now because it contains all of my working data.