Rebuild index task failed with error: Could not proceed with index DDL operation on table because it conflicts with another concurrent operation

Hi Friends,

I have one rebuild index job in my environment which is created using maintenance plan & having an option "keep index online ".

job is continuously failed at this schedule time, when i saw maintenance plan history then i got following error.

Error :

Executing the query "ALTER INDEX [IX_CMSID] ON [dbo].[tblAccountFacility]" failed with the following error: "Could not proceed with index DDL operation on table 'tblAccountFacility' because it conflicts with another concurrent operation that is already in progress on the object. The concurrent operation could be an online index operation on the same object or another concurrent operation that moves index pages like DBCC SHRINKFILE.". Possible failure reasons: Problems with the query, "ResultSet" property not set correctly, parameters not set correctly, or connection not established correctly.

details:

The above mentioned index which causing an error is non-clustered index, use page lock option is enable.

database size is only 8.00 GB,, Autoshrink option is=false

SQL server is 2008 SP2

Please help me how to sort this problem.