These files consuming high cpu on the server Because of that you are facing this issue.
i suggest you to update plugin themes and optimize the domain scripts frequently as well
Did you do this?
Are you running the latest and greatest
Are you running excisive plugins that aren't helping
Are your plugins and style made with quality code?
Temporally disable all your plugins and use the default style.
Does that help?
If so add one plugin at a time and stop with your cpu crashes.
Oh... and ofc you'll need to have showthread.php spelled correctly, wouldn't hurt to upload a fresh copy of your vb files as well.
Take a backup
The host isn't 100% at fault here, they are trying to help. Your site is bogging the server down, it's very likely a poorly coded plugin.