I solved this issue with the following steps:
1.- drop table customer_grid_flat
2.- Re-create table:
CREATE TABLE IF NOT EXISTS customer_grid_flat
(
entity_id
int UNSIGNED NOT NULL COMMENT 'Entity ID' ,
name
text NULL COMMENT 'Name' ,
email
varchar(255) NULL COMMENT 'Email' ,
group_id
int NULL COMMENT 'Group_id' ,
created_at
timestamp NULL default NULL COMMENT 'Created_at' ,
website_id
int NULL COMMENT 'Website_id' ,
confirmation
varchar(255) NULL COMMENT 'Confirmation' ,
created_in
text NULL COMMENT 'Created_in' ,
dob
date NULL COMMENT 'Dob' ,
gender
int NULL COMMENT 'Gender' ,
taxvat
varchar(255) NULL COMMENT 'Taxvat' ,
lock_expires
timestamp NULL default NULL COMMENT 'Lock_expires' ,
shipping_full
text NULL COMMENT 'Shipping_full' ,
billing_full
text NULL COMMENT 'Billing_full' ,
billing_firstname
varchar(255) NULL COMMENT 'Billing_firstname' ,
billing_lastname
varchar(255) NULL COMMENT 'Billing_lastname' ,
billing_telephone
varchar(255) NULL COMMENT 'Billing_telephone' ,
billing_postcode
varchar(255) NULL COMMENT 'Billing_postcode' ,
billing_country_id
varchar(255) NULL COMMENT 'Billing_country_id' ,
billing_region
varchar(255) NULL COMMENT 'Billing_region' ,
billing_street
varchar(255) NULL COMMENT 'Billing_street' ,
billing_city
varchar(255) NULL COMMENT 'Billing_city' ,
billing_fax
varchar(255) NULL COMMENT 'Billing_fax' ,
billing_vat_id
varchar(255) NULL COMMENT 'Billing_vat_id' ,
billing_company
varchar(255) NULL COMMENT 'Billing_company' ,
PRIMARY KEY (entity_id
),
INDEX CUSTOMER_GRID_FLAT_GROUP_ID
(group_id
),
INDEX CUSTOMER_GRID_FLAT_CREATED_AT
(created_at
),
INDEX CUSTOMER_GRID_FLAT_WEBSITE_ID
(website_id
),
INDEX CUSTOMER_GRID_FLAT_CONFIRMATION
(confirmation
),
INDEX CUSTOMER_GRID_FLAT_DOB
(dob
),
INDEX CUSTOMER_GRID_FLAT_GENDER
(gender
),
INDEX CUSTOMER_GRID_FLAT_BILLING_COUNTRY_ID
(billing_country_id
),
FULLTEXT FTI_8746F705702DD5F6D45B8C7CE7FE9F2F
(name
, email
, created_in
, taxvat
, shipping_full
, billing_full
, billing_firstname
, billing_lastname
, billing_telephone
, billing_postcode
, billing_region
, billing_city
, billing_fax
, billing_company
)
) COMMENT='customer_grid_flat' ENGINE=innodb charset=utf8 COLLATE=utf8_general_ci