I've try to migrate a website in Joomla from 1.5 to 2.5 using jUpgrade but I've receive the "undefined migrating" error.

The files was correctly transferred, but there's no change to the db, and when I try to log on website.com/jupgrade, I land on a page saying "please delete installation folder" and no db was transferred/created (so I have to create it manually and create menu, article, etc. wasting so much time!)
Please help. I have already tried removing folder and changing tmp to 777 permission (with chmod) and nothing changed!
**Update: 2012-07-24 Getting more information while running jupdate in debug mode:
"========== [checks]
1
========== [cleanup]
1
========== [decompress]
1
========== [install_config]
========== [install_db]
========== [undefined] [undefined]
jos-Error: Table 'name_joomla.j25_users' doesn't exist SQL=INSERT INTO
j25_users(id,name,username,password,usertype,block,sendEmail,registerDate,lastvisitDate,activation,params) VALUES ('62','Administrator','admin','[email protected]','d7bfdb4f0aa91c9618b2969f4b91006e:jJzEVXG7VDz0u95RQu06CQPMFsxCic4e','Super Administrator','0','1','2011-12-16 14:37:40','2012-07-24 13:57:43','','{\"admin_language\":\"\",\"language\":\"\",\"editor\":\"\",\"helpsite\":\"\",\"timezone\":\"UTC\"}') "
Help >> System Information >> Directory Permissionsand make sure all the folder mentioned are "writable" - Lodder