Por si sirve de algo, he visto esto en el webconfig...
Código:
<globalization requestEncoding="iso-8859-1" responseEncoding="iso-8859-1"/>
<membership defaultProvider="AspNetSqlProvider">
<providers>
<add name="AspNetSqlProvider" type="System.Web.Security.SqlMembershipProvider" connectionStringName="ASPNETDBConnectionString" requiresQuestionAndAnswer="false" requiresUniqueEmail="true" passwordFormat="Hashed" minRequiredNonalphanumericCharacters="0" minRequiredPasswordLength="3"/>
</providers>
</membership>