I get an error when I try to create an index on an existing table.

The error:
Error on rename of '.\DESCRIPTION' to '.\#sql2-964-1' (errno: 121).

If I create the index inside the creation of the table it works fine.
Also if I wait for a while or restart the server the index can be created with no problem.

Please can anyone advice me on this? I cant find any simular cases on the internet.