“500” errors, server crash and redirect errors

Hello all

On my WP multisite server with 200+ sites in subfolders, I am experiencing a lot of different errors.

Problem overview
1) “500” error (possibly linked to the “PHP Fatal error: Allowed memory size of 268435456 bytes exhausted” that I see in my apache log)
2) Server crashes every 3-4 days.
3) Getting several thousand “Request exceeded the limit of 10 internal redirects due to probable configuration error” errors a day in my apache log.

Problem description
1) To try and fix this issue I have tried allocating as much as 1GB! of RAM in the PHP.ini file and in the wp-config.php file but to no avail. The server is bran new with 16GB RAM and 2 Zeon processors and is only handling this one site.
The error occurs in network admin when trying to add users to a site or viewing installed themes. Other places will generate the error as well but not consistently. I have tried removing all plugins but “WordPress MU Domain Mapping” plugin which I can’t do without but still get the errors.

2) The server crashes every 3-4 days with no real consistency. According to my server monitor system, it uses all available RAM and SWAP memory and stops reacting to requests. I have been going through the log files and nothing unusual is happening just before a crash. I have tried restarting the apache a few times a day which seems to reduce the frequency of the crashes. I also tried moving to another server but the problem remains.

3) The “Request exceeded the limit of 10 internal redirects due to probable configuration error” errors are filling my log at an enormous rate. This problem is well described on www.ads-software.com and other places but I can’t find a solution.

After having spent more than 2 weeks on this I am really hoping you can help me shed some light on the real reasons for the issues.