undefined LOG_LEVEL_FATAL, weird

Hi, I'm getting a lot of these errors logged:

Sep 19 12:00:52 host httpd: PHP Fatal error: Undefined class constant 'LOG_LEVEL_FATAL' in /var/www/vhosts/.../httpdocs/core/model/modx/modx.class.php on line 2049
Sep 19 12:01:42 host last message repeated 3 times

where php is saying a modx class constant is not defined...I've tried putting some error_log() calls but I get 500 server errors (and no log) if I log much or if I try seeing if modX::LOG_LEVEL_FATAL is defined, such as:
error_log("no log level fatal defined!, " . $msg . "\n " . print_r(debug_backtrace(), true));

How could the code be here and not have class constants defined?
Running latest Revo 2.1.3, php 5.3.3
thanks for any advise on debugging this,
---avibodha

Turn off APC or eAccelerator caching.

right on the mark, thanks!
APC was the culprit, using latest version, 3.1.9.

only happens in manager so I'll try just disabling for /manager

thanks much

UPDATE - nope, must totally disable APC, otherwise assorted weird errors [ed. note: avibodha2 last edited this post 15 years ago.]

I encountered this today, any pointers why MODX doesn't play nice with APC? The system requirements page still lists it as recommended; is there a buggy version of APC or another issue involved? I've looked for a ticket but not found one.