Thanks, it was a problem with my .htaccess file. The following line was the problem:
Customer support commented it out and replaced it with this:
That got my page to load properly but caused server side includes to stop working on my .htm and .html pages so I commented out that replacement line as well.
Here's what's in my current .htaccess file:
I suspect that the change to my .htaccess file occurred when I was installing an xml include in one of my directories which only seems to work with .php pages. Interestingly enough, the xml include seems to be working just fine without it.
Out of curiosity, could you tell me what exactly those commented out lines are supposed to do? Any idea why the first one "broke" my site and the second one caused server side includes to stop working for me?
In any case, thanks and I hope this information proves helpful to someone in a similar situation in the future.