custom provider causes invalid password error

i have created a custom provider in web.config
<membership defaultProvider="CustomisedProvider">

<providers>

<clear/>

<add name="CustomisedProvider"

type="System.Web.Security.SqlMembershipProvider"

applicationName="KalsAp"

connectionStringName="mySqlServer"

minRequiredPasswordLength="5"

minRequiredNonalphanumericCharacters="0"

requiresQuestionAndAnswer="false"

requiresUniqueEmail="false"

passwordStrengthRegularExpression=""


/>

</providers>


and when i try to add a user - i get the error password must comply with
password strength in default provider

any help please

Kal