Upgrading Drupal

Hello,

I've tried to migrate from drupal 6.26 to drupal 7.14 5 times, but no success.
at the middle of conversion I receive this error....

After Update D6 to D7 Getting Error Fatal error: Call to undefined function jquery_ui_add() Can't solve any one can advice me

Recently we upgrade drupal from 7.8 to 7.14, then the main menu on the top navigation not working. We use superfish module (7.18 )to display our three level menus, we only display the items on the first level menu. But each time we add a node, the items on the second level menu just jump to first level and show up on the top navigation, it is very strange, can some body please help?

I check the weight and relationship on taxonomy, it is ok, but on the menu, the item's relationship in the same taxonomy just change (second level become to first level)

I am getting following error again and again while upgrading from drupal 6.26 to drupal 7.14 .

taxonomy module

I upgraded today from 7.7 to 7.14 and somehow in the shuffle of it all, my Fields UI tabs are no longer displaying. Anywhere. I've uninstalled and reinstalled Fields UI, uninstalled Overlay, even went as far as restoring all my files and the database to 7.7. Still nothing.

How is it possible that a core module can simply disappear like this?

Hi,
We r about to convert version 4 Drupal website to Version 7 Drupal website.May I know the best procedure for the conversion ?I also wanted to know the factors to be taken care off,when upgarding the existing drupal website to verison 7 drupal sites.Thanks in advance

Thanks