Aruba-MySQL: can't create/change table to engine=INNODB
Take a look at the InnoDB Internals (Picture from Percona CTO Vadim Tkachenko)



Please note the data dictionary inside ibdata1 (the system tablespace)

It sounds like you have a broken data dictionary entry on the task table when it existed

The only way around would be move all the tables into another database.

For starters, suppose you have database mydb1. Create another database mydb2

CREATE DATABASE mydb2;


For example, to move mydb1.mytable into mydb2, do this

ALTER TABLE mydb1.mytable RENAME mydb2.mytable;


Move all your tables sideways into mydb2.

You would then have to drop your old database

DROP DATABASE mydb1;


You should be able to convert the task table in mydb2 into InnoDB.

USE mydb2
ALTER TABLE `task` ENGINE = INNODB;


Give it a Try !!!