Odd problem

For the first time, I just had a problem on the forum that I have been experiencing repeatedly with a web host that we use at work for several projects. I don't know the Dev Shed setup but the web host uses php in su-exec.

The problem is this. On scripts that do a lot of processing (the definition of "a lot" seems to vary), occasionally requesting that page causes the browser to ask if you want to "download" the php file.

In this case, I was replying to a post in the PHP forum when this happened. This is the first time I had seen this outside of the web host we work with. What's even weirder, is that it wanted to view the file in Excel! In addition smiley icons, last post icons, rep icons, IM icons and graphics for "new post" and other buttons are not appearing (which has actually happened several times). I finally had to click on "Preview Post" instead of submitting it, in order to make it work. The problem seems connected to server load sometimes, but I can't be sure.

Nobody at the web host (sigh you know what, I'm so fed up with them I'm just going to name them "Site 5") can tell me what is going on. If you guys have this figured out, I would love to hear what is causing this and if there is a solution.