3
Also make sure you are using modules compatible with 2.5.4. You may want to test them on a server at home to make sure. There are a number of modules that need to be tweaked to work with the 2.5 series. Could be a bug with 2.5 or a bug with the module. But you want to make sure you can run the modules on a test server before you put them on a live server.
Also check that the mysql and php versions are more recent as well.
Otherwise as chefry said, make sure all the files are there.
Attending College working towards Bachelors in Software Engineering and Network Security.