Very strange website behavior

My client's site has been up and running for a year and a half now without any issues. In the past week, we have added a coupon code and edited some ez pages (checked html code and it is all ok). After that point and I'm not sure if this was the defining point, the website has been alternating between running perfectly fine and displaying the initial zencart setup page ("Hello. Thank you for loading Zen Cart™. You are seeing this page for one or more reasons:............................"). I have talked to GoDaddy the host and they can not replicate the issue and therefore cannot help me. I have also found that on cell phones (but not on my wifi ipad and laptop), the site has no issues displaying.

I am running 1.3.9 on a linux server.
The site has never been upgraded.
Any addons I may have installed I did a year ago and they did not affect the site at that time.
The url is http://shopskm.com.
GoDaddy is the hosting company. I have several clients at GoDaddy and a few running zencart without current issues.

So I am answerless and bewildered at this point. I would love any possible ideas.

Several GoDaddy customers have been reporting the same symptoms in the last couple weeks.
Sounds like they're having problems with their servers.