When you upgrade your Magento to 1.4 then some strange stuff can happen.
First read the upgrade notes.
Secondly a note about .htaccess files that Magento 126.96.36.199 installs. For example Estonian hosting provider Zone does not support php directives in the .htaccess files.
If you get ”
Internal Server Error
” or similar after upgrade using Magento Connect then check your .htaccess file in / folder. Very likely Magento upgrade has overwritten it and the php directives are there. Comment those out if these are not supported by your hosting provider.
Refresh the page and it should work. Voila!:)
If you see something like “Exception during cache and session cleaning: Invalid mode for clean() method” then remove app/code/core/Zend/Cache/Backend folder.
After you’re back in the admin of 188.8.131.52 be sure to flush and refresh all indexes and cache. Don’t enable any caching at this point yet.