We're having strange behavior on our linux server. Here are some symptoms:
1) PHP using old information when processing scripts: For example: I loaded up the site today and it ran the mobile version of our Joomla 2.5.9 template instead of the normal template. I looked through the access log and two minutes before I loaded the site up an iPhone had accessed the site. So, for some reason the PHP code ‘thought’ that my access was still the iPhone. Here’s a snip from the access log.
188.8.131.52 - - [01/Mar/2013:07:39:24 -0800] "GET / HTTP/1.1" 200 9771 "https://m.facebook.com" "Mozilla/5.0 (iPhone; CPU iPhone OS 6_1 like Mac OS X) AppleWebKit/536.26 (KHTML, like Gecko) Mobile/10B141 [FBAN/FBIOS;FBAV/5.5;FBBV/123337;FBDV/iPhone2,1;FBMD/iPhone;FBSN/iPhone OS;FBSV/6.1;FBSS/1; FBCR/AT&T;FBID/phone;FBLC/en_US;FBOP/0]"
184.108.40.206 - - [01/Mar/2013:07:43:45 -0800] "GET / HTTP/1.1" 200 9771 "-" "Mozilla/5.0 (Windows NT 6.1; WOW64; rv:19.0) Gecko/20100101 Firefox/19.0"
2) Links on the site are sometimes being generated within Joomla differently: sometimes "ww.sitename.com" or just "sitename.com" when it should be "www.sitename.com".
3) When I make a configuration change to the site (within Joomla administration), it doesn't always take immediately, though it should. For instance, when click publish something using the user interface, it will still be published for quite a while after I unpublished it. During a problem like this, I have tried restarting both Apache and MySQL and it didn't help. I had to wait until something updated. Eventually it does update.
4) The php session doesn't consistently work. We have code that generates a captcha from a session variable. The code fails sometimes rendering the captcha inoperable.
All the above is totally inconsistent. Sometimes it wigs out other times it doesn't. Also, note that the site works totally fine on our dev.sitename.com. We even tried to switch the Apache webserver configuration from our dev.sitename.com to our sitename.com. And the problem still persists. Lastly, our Joomla cache is turned off.