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 1.4.0.1 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 javascript does not work or product image uploads fail, then be sure to check .htaccess file in media folder.  So open .htaccess form media folder and comment out all directives from there.

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 1.4.0.1 be sure to flush and refresh all indexes and cache. Don’t enable any caching at this point yet.

In case you have configured a custom URL for your Magento admin, then you may have problems with otherwise great Magento extension for changing attribute sets. Flagbit has developed good extension “Change Attribute Set” that enables to change attribute sets for the products. However they have hardcoded URL for admin (/admin). Many people including me use customized URL for Magento admin for different reasons: security, localization …

The extension does not work properly if you use admin URL different than /admin. Fortunately there is a fix, so I just repeat it here to make it clear.

Open the extension’s config file: app/code/community/Flagbit/ChangeAttributeSet/etc/config.xml

Find XML fragment <from><![CDATA[#^/admin/catalog_product/changeattributeset/.*#]]></from>

Change string admin to your customizes URL. For example <from><![CDATA[#^/my_admin_url/catalog_product/changeattributeset/.*#]]></from>

That’s it! Enjoy!

This is a simple tip that could help you in case when you cannot login to Magento Admin after database migration.

Sometimes it happens that you need to move your whole Magento database from one site to another. Let’s say you want to copy your production database to your testsite. Everything goes well, you copy all data but you cannot login to admin of your test Magento… You use correct admin password, the same that you use for the production site. Still nothing…

OK, here are the clear steps to check before you start. You need to check and change a few fields in Magento configuration that is stored in database:

in table “core_config_data” check the following fields:

web/unsecure/base_url – set this to your testsite URL
web/secure/base_url – set this to your testsite URL
web/cookie/cookie_domain (this one got me once… ) – better set it to empty
web/cookie/cookie_path – better set it to empty

After that remove cache – delete var/cache folder.

Please leave us a comment if this post helped you or if you have anything to add here.