MySQL - Unable to create column

I am using MySQL 5.1. When i am trying to add new column, it throws error like this,

Database name is "ebill".

Error Code : 1025
Error on rename of '.\ebill\#sql-98_477' to '.\ebill\user' (errno开发者_如何转开发: 150)
(0 ms taken)

This is my sql query:

alter table `ebill`.`user` add column `User_Password` varchar(25) NULL

Where is the issue?

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