Description:
CREATE TABLE `tipoveiculo` (
  `tipo_veiculo` varchar(20) NOT NULL,
  PRIMARY KEY (`tipo_veiculo`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;

Values in the table 
'Automovel 2'
'Moto'

When i change Moto to Moto_Bla no problem

When i try to change 'Automovel 2' to 'Automovel 3' gives me these error

'the maximum row size for the used table type not counting blobs...'

"sometimes it work sometimes he doesn´t" also trying to force changes makes the mysql server to stop service

How to repeat:
I don´t know it just append sometimes....

Suggested fix:
Some sql code to check the entire database for inconsistences

Please try version 5.5.21. Thanks.

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mysql> use test
Database changed
mysql> CREATE TABLE `tipoveiculo` (
    ->   `tipo_veiculo` varchar(20) NOT NULL,
    ->   PRIMARY KEY (`tipo_veiculo`)
    -> ) ENGINE=InnoDB DEFAULT CHARSET=utf8;
Query OK, 0 rows affected (0.17 sec)

mysql> insert into tipoveiculo values ("Automovel 2");
Query OK, 1 row affected (0.06 sec)

mysql> insert into tipoveiculo values ("Moto");
Query OK, 1 row affected (0.02 sec)

mysql> update tipoveiculo set tipo_veiculo = "Automovel 3" where tipo_veiculo = "Automovel 2";
Query OK, 1 row affected (0.06 sec)
Rows matched: 1  Changed: 1  Warnings: 0

mysql> select * from tipoveiculo;
+--------------+
| tipo_veiculo |
+--------------+
| Automovel 3  |
| Moto         |
+--------------+
2 rows in set (0.01 sec)

mysql>

You can see the garbage that goes into table when bug append

Attachment: MysqlUpdateBug.JPG (image/jpeg, text), 185.58 KiB.

please upload the entire mysql error log. innodb should print alot of error messages there.  compress it if it's large.

thanks,

Where are the logs??

Error log is usually named <hostname>.err and is located in the datadir (see your my.cnf or my.ini file content). We need to know what OS do you run MySQL on to be more specific.

No feedback was provided for this bug for over a month, so it is
being suspended automatically. If you are able to provide the
information that was originally requested, please do so and change
the status of the bug back to "Open".