[TYPO3-install] backend not loading all sys ext after upgrade - downgrade

[Jaco Graaff]

I did a full backup of all files
then tried to upgrade to 6.2 from 6.1.6
to many errors like tt_address
manual updating the extensions did not help
so I reverted back
now the front does not work
install tool loads correct but backend show without styles and icons
-------------------------------------------
most of the backend modules are missing: eg: view, pagetree, template, 
workspaces, access, function, ....etc
-------------------------------------
The pagteree shows blank
---------------------------------------
upgrade through wizard says
---------------------------------------
Install the new TYPO3 Skin "t3skin"
Array
Next
---------------------------------------
on next:
wrong parameter
------------------------------------------
The backend skin "t3skin" is not loaded. TYPO3 4.4 introduced many 
changes in backend skinning and old backend skins are now incompatible. 
Without "t3skin" the backend may be unusable. Install extension "t3skin".

--------------------------------------------------