Ok then, brand new server, P4, 2.66, running RH9 (2.4.20-28.9) and RAID. After 3 month without problems I found this in the logs this morning. Anyone?
kernel: Page has mapping still set. This is a serious situation. However if you
kernel: are using the NVidia binary only module please report this bug to
kernel: NVidia and not to the linux kernel mailinglist.
kernel: ------------[ cut here ]------------
kernel: kernel BUG at page_alloc.c:122!
kernel: invalid operand: 0000
kernel: w83781d eeprom i2c-proc i2c-isa i2c-i801 i2c-core ipt_mark ipt_MARK ipt_TOS iptable_mangle ip_conntrack_ftp ip_conntrack_irc ipt_unclean ipt_REJECT ipt_LOG ip
kernel: CPU: 0
kernel: EIP: 0060:[<c013618b>] Not tainted
kernel: EFLAGS: 00010282
kernel:
kernel: EIP is at __free_pages_ok [kernel] 0x307 (2.4.20-28.9)
kernel: eax: 00000033 ebx: 00001000 ecx: 00000001 edx: f56bc000
kernel: esi: c1a9e768 edi: 00000000 ebp: d13758c8 esp: e3075ed8
kernel: ds: 0068 es: 0068 ss: 0068
kernel: Process mysqld (pid: 16301, stackpage=e3075000)
kernel: Stack: c023ea20 c023e9c0 c023e960 00000d01 00000d41 c108ee6c 0000001f 00000000
kernel: 00000d50 c1a9e768 00051000 00001000 c1a9e768 d13758c8 00000d51 c012ce28
kernel: e3075f7c c1a9e768 00000000 00001000 00001000 00000001 00000000 00000000
kernel: Call Trace: [<c012ce28>] do_generic_file_read [kernel] 0x228 (0xe3075f14))
kernel: [<c012d2f8>] file_read_actor [kernel] 0x0 (0xe3075f40))
kernel: [<c012d424>] generic_file_read [kernel] 0xa8 (0xe3075f60))
kernel: [<c012d2f8>] file_read_actor [kernel] 0x0 (0xe3075f70))
kernel: [<c013cbf4>] sys_read [kernel] 0x84 (0xe3075f9c))
kernel: [<c0108d7b>] system_call [kernel] 0x33 (0xe3075fc0))


The mobo is a Tyan S2099GNNR

Your error looks similar to the below link about kernel BUG at page_alloc.c:122
http://www.cs.helsinki.fi/linux/linux-kernel/2003-23/1223.html

Strange enough, it happened only once (today) when another server attempted to login to make the nightly backup. Rebooted the box, rerun the backup and the problem seems to be gone.

Also, the board has an builtin ATI, not Nvidia. http://www.tyan.com.tw/products/html/trinityi845e.html