Mysqld Using 100 Percent Of Cpu

I've got a strange situation here. We have some software which we run on multiple servers. As of today the software is using 100 percent (sometimes more) of the cpus.

Here is the result from top. It's usually far worse using 100 percent of both cpu's almost all of the time. I just restarted, but the server load is climbing to 20+. Any idea how I can figure out what is going on? The same software on two other identically configured servers runs fine. This server has had no problems for over 6 months, but suddenly this started today. The server is a dual opteron with 4GB of ram. The databases are innodb thus the high memory usage for mysql (innodb buffer pool size)

top - 13:52:54 up 3:14, 2 users, load average: 3.39, 4.42, 6.86
Tasks: 121 total, 4 running, 108 sleeping, 9 stopped, 0 zombie
Cpu(s): 66.1% us, 1.7% sy, 32.2% ni, 0.0% id, 0.0% wa, 0.0% hi, 0.0% si
Mem: 4090568k total, 3077004k used, 1013564k free, 52748k buffers
Swap: 2096440k total, 56k used, 2096384k free, 1796632k cached

PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
11871 mysql 15 0 2581m 1.0g 3844 S 96 26.2 13:05.73 mysqld
7569 root 39 19 8048 2024 1304 R 65 0.0 32:27.49 http
11984 apache 15 0 152m 14m 5860 S 12 0.4 0:24.27 httpd
11990 apache 15 0 152m 17m 8376 S 9 0.4 0:14.31 httpd
12002 apache 16 0 153m 15m 5408 R 6 0.4 0:08.60 httpd
12040 apache 15 0 152m 17m 8524 S 5 0.4 0:03.86 httpd
11966 apache 15 0 153m 17m 8280 S 3 0.4 0:22.99 httpd