Since you decided to post your issue in someone else's thread, I would hope that you actually read through the thread and considered the suggestions given to the previous poster.
However, I see no evidence in your post which suggests you've done anything to inspect the root cause yourself.
ie: what happened when you followed my suggestions posted as the first reply to the original poster?
Quote Originally Posted by DrByte View Post
I'd start by using FTP to download a complete copy of all the files on your site.
Then use WinMerge to compare them with your working files already on your PC. Make sure there's no corruption in any of the files and that nothing has been hacked in them.
Then do a comparison against a freshly-downloaded-and-unzipped copy of the same version of Zen Cart ... just to be sure it wasn't caused by an edit you did in your own working files. Naturally your customizations will be different, but need to be looked at carefully.

You could also ask your host if (during the time of the overload) there were any extremely-slow-running MySQL queries or excessive numbers of unclosed MySQL connections from your account?
Also, as Kim mentioned, is your site fully patched? All forum members were emailed about an important security patch back in June 2009.
And, a list of important patches is prominently posted in the News area, as well as at the top of every forum section.

Also, I notice that all the URLs from the logs you posted, are not standard URLs generated by Zen Cart. Thus, you've got some sort of addon involved too. Perhaps turning that off, and maybe several others too, might help you isolate where some of the performance bottlenecks are for you.

If your hosting account has NOT been having these performance problems previously, then you've likely installed an addon that's causing you problems, or you've been hacked.
Only *you* can figure that part out.

http://www.zen-cart.com/wiki/index.p...ing_From_Hacks

It could also be that you've been having these problems all along, causing some server problems for the hosting company, and maybe the hosting company has just recently turned on some performance monitoring and your site suddenly came up in their first analysis, thus making you their first candidate to slap around. Either way, you'll need to narrow down the problem by working up a list of differences between your site and a brand new clean uncustomized install, and sort out whatever you've got that's breaking things.