This is a SalesForce.com error. Salesforce provides the following information on their site:

This is something temporary and would be fixed automatically in 10-15 minutes maximum.
Some common causes are -
  1.  Sharing Rules are being calculated.
  2. A picklist value has been replaced and replacement is in progress.
  3. A custom index creation/removal is in progress.
  4. Someone else is already editing the same record that you are trying to access at the same time. This could be a data process, such as an upload.

https://help.salesforce.com/apex/HTViewSolution?urlname=Email-to-Case-error-UNABLE-TO-LOCK-ROW-unable-to-obtain-exclusive-access-to-this-record&language=en_US

Additional information here: https://developer.salesforce.com/forums/ForumsMain?id=906F00000008qfTIAQ

If you can commit the batch again, go ahead and do so. Otherwise, you'll need to re-enter these gifts into a new batch or create them as individual donations.

Note: We provide links to third-party websites in an effort to help you resolve your issue. We are not responsible for the information on third-party websites, and we cannot assist with implementing the resolution from these websites.