FYI - I had several issues and hope this info will help.
PHP Version and Test
Not sure about other hosts, but 1 and 1 Hosting leads you to believe you are using PHP 5, but very likely it's a version of PHP 4. This creates all kinds of issues. To test, create a new file in Notepad, paste this simple line of code, "<?php phpinfo(); ?>" (without the quotes) and save as "test.php" (without the quotes). Upload to your root directory - then type the following into your browser, "www.yourdomain.com/test.php" and you will find what version you are actually using. Replace "yourdomain" with your own domain name.
Correct PHP Version Issues with .htaccess file
Create a new file in Notepad if you do not have an .htaccess file already. Place this line of code in it, "AddType x-mapp-php5 .php" (without the quotes) and save the file as .htaccess - be sure there is no .txt - ONLY ".htaccess". Upload the file to your root directory. Basically, this just tells your files to use PHP 5.
Automatic Updates & Plugin Issues – Memory Issues – PHP.ini file
If you try to update WP automatically or install/activate plugins and all you see is "unzipping", "unpacking" or something similar - essentially nothing really happens, it is very likely you do not have enough memory allotment to execute.
You may also experience “500 Internal Server Error….” when working with plugins – or nothing appears after you activate a plugin on page/post editors, etc.
If you have or can access your php.ini file, check to see the “memory_limit” or “upload_max_filesize” – if you don’t have a “php.ini” file, create one in Notepad and insert the following:
memory_limit = 100M
upload_max_filesize = 192M
post_max_size = 100M
file_uploads = On
Save/upload to your root directory. I also included it in my wp-admin folder just in case.
Plugins and “500 Internal Server Error”
If you are stuck with a “500 Internal Server Error” on your screen when dealing with plugins – try going back on your browser and check the “deactivate all” box and apply. If you can’t get back, go to your “Plugins” folder and just rename it briefly – i.e. “plugins5” – that will automatically deactivate all your plugins – go back to your admin area and check installed plugins – you should be able to access everything again. You can now try activating one plugin at a time to see if there’s a conflict, OR it may just be a memory issue – see above.
FYI – I am not a programmer – I spent 3 days uploading, installing/reinstalling WordPress and activating/deactivating plugins, ftp uploads, etc on 3 blogs and searching Google and any other source I could find until I discovered this info.
Please feel free to correct anything you feel is incorrect – this is just what worked for me. Hope this helps someone else’s frustration.