I keep getting system messages instead of webpages

Thanks in advance for reading through and offering me some suggestions:

I have a brand new install of elgg 1.8.8 on my MediaTemple shared web hosting. I managed to go through the installation wizard with no problems (well, I got a warning about open_basedir setting, but I see things are being written in the data directory, so I assume the warning is not an issue).

When I navigate the installation I often (but not always) get system messages rather than web pages.

I have tried:

*re-downloading the installation from elgg and deleting/redoing the installation from scratch

*changing where I install

*deleting/recreating the database & reinstalling

*disabling plugins

...and 2 days later I am stumped.

Like I said, it doesn't always give a system message, sometimes it works correctly. So you might have to register and use the site for a bit to see what I'm talking about. Here are some examples of system messages I get:

When I go to the home directory:


When I invited myself to join (different email accounts):

{"output":"","status":0,"system_messages":{"error":[],"success":["Your friends were invited."]}}

Does anyone have any ideas what I'm doing wrong? The website is located here: