Invalid character in a Base-64 string

I am getting this error when I am validating the 开发者_开发技巧user with sql membership provider

this.provider.ValidateUser(userName, password); the password i have used is "freetrial". I tried trimming the spaces but still no luck!!!

and the call stack is as follows:

[FormatException: Invalid character in a Base-64 string.]
   System.Convert.FromBase64String(String s) +0
   System.Web.Security.MembershipProvider.EncodePassword(String pass, Int32 passwordFormat, String salt) +54
   System.Web.Security.SqlMembershipProvider.CheckPassword(String username, String password, Boolean updateLastLoginActivityDate, Boolean failIfNotApproved, String& salt, Int32& passwordFormat) +169
   System.Web.Security.SqlMembershipProvider.CheckPassword(String username, String password, Boolean updateLastLoginActivityDate, Boolean failIfNotApproved) +42
   System.Web.Security.SqlMembershipProvider.ValidateUser(String username, String password) +78

I got it working..it is internal legacy import issue.