The CPU usage is in userspace so I am guessing it is a stuck PHP task or similar.
If it was hardware/IO problems you would see a higher 'wa' percentage.
I have only seen this happen with one PHP script that had a very bad implementation of AJAX.
You can look in the error log first. Then if you look in /proc/26807/ using ls -l and its subdirs it may give you a better clue of what is going on, beyond that you may need to break out gdb.
Andrew Hutchings (A-Wing) - Linux Jedi A-Wing Internet Services
Windows is the path to the darkside...Windows leads to Blue Screen. Blue Screen leads to downtime. Downtime leads to suffering...I sense much Windows in you.
See mod_status documentation at httpd.apache.org/docs/1.3/mod/mod_status.html
Then you can point your broser to h__p://machine/server-status and see (among others) table with PID of server process, requested VHost and requested URLs. With this you can find out buggy script or url or something.
BTW, individual apache processes can be killed independed of each other, so no need to restart whole webserver.
(Damned forum SW: it is really helps in technical discussion if you cannot use hyperlinks)