The Web host has already found the problem, and is now solved. Thanks to Ploghost for finding the problem as fast as they can.

<Technical description - ignore>
The problem was traced to a seemingly wayward WordPress plugin that has inserted rows upon rows of data into the database. Once the plugin code is executed, these rows of data are loaded into memory, severely stressing the server into submission (ie., crash). The offending plugin has been removed and will never be used again.
<End technical description>

Apologies to the faithful readers. If you, dear readers, encounter more problems, please leave a message at the chat box at the side bar. Thank you.