Error 500 "Internal Server Error" in WebAsyst Installer or after login to account

When trying to open WebAsyst Installer or log in to a WebAsyst user account error message 500 "Internal Server Error" may appear in your browser. This message means that the remote server was unable to generate the requested page. Most frequently encountered cases when such error may occur are described below.

• Less than 32 MB memory are available on the server. Ensure availability of at least that amount of memory. Change the value of PHP parameter memory_limit accordingly if necessary.
• WebAsyst configuration contains a memory usage limit which is below 32 MB. That limit value can be changed manually in file kernel/wbs.xml through modification of parameter MEMLIMIT in the following line:

  <SYSTEM COMPANY="company" LICENSE="" MEMLIMIT="64"/>

  If you leave that value empty, default memory usage limit of 32 MB will be applied.
• Permissions of directory kernel/includes/smarty/compiled/ and its contents do not allow the web server to modify their contents. Either grant the web server full access rights to that directory and its contents or completely empty out directory kernel/includes/smarty/compiled/ and change its permissions to make it web server writable.