What does this message mean? Also, help with panics

[Alex Povolotsky]

Aug 22 17:46:48 mest /kernel: xl0: transmission error: 90
Aug 22 17:46:48 mest /kernel: xl0: tx underrun, increasing tx start threshold to 120 bytes

I'm getting it on a server that suddenly become unstable, it keeps crashing under LA 10+ (no nesessary crash under 10+, and sometimes crashes under less load).

Here are three last panic messages:

Fatal trap 12: page fault while in kernel mode
fault virtual address   = 0x8
fault code              = supervisor read, page not present
instruction pointer     = 0x8:0xc0196537
stack pointer           = 0x10:0xd7c2dd78
frame pointer           = 0x10:0x0
code segment            = base 0x0, limit 0xfffff, type 0x1b
                        = DPL 0, pres 1, def32 1, gran 1
processor eflags        = interrupt enabled, resume, IOPL = 0
current process         = 5 (syncer)
interrupt mask          = none
trap number             = 12
panic: page fault

(kgdb) where
#0  0xc015b4fa in dumpsys ()
#1  0xc015b314 in boot ()
#2  0xc015b69c in poweroff_wait ()
#3  0xc02607f6 in trap_fatal ()
#4  0xc02604b5 in trap_pfault ()
#5  0xc0260087 in trap ()

IP points to spec_vnoperate


Fatal trap 12: page fault while in kernel mode
fault virtual address   = 0x4
fault code              = supervisor write, page not present
instruction pointer     = 0x8:0xc025d94d
stack pointer           = 0x10:0xdade5e3c
frame pointer           = 0x10:0xdade5e4c
code segment            = base 0x0, limit 0xfffff, type 0x1b
                        = DPL 0, pres 1, def32 1, gran 1
processor eflags        = interrupt enabled, resume, IOPL = 0
current process         = 98602 (httpd)
interrupt mask          = net tty bio cam 
trap number             = 12
panic: page fault

(kgdb) where
#0  0xc015b4fa in dumpsys ()
#1  0xc015b314 in boot ()
#2  0xc015b69c in poweroff_wait ()
#3  0xc02607f6 in trap_fatal ()
#4  0xc02604b5 in trap_pfault ()
#5  0xc0260087 in trap ()
#6  0xc025d94d in pmap_insert_entry ()
#7  0xc025e8dc in pmap_copy ()
#8  0xc0223b36 in vm_map_copy_entry ()
#9  0xc0223d37 in vmspace_fork ()
#10 0xc0220faf in vm_fork ()
#11 0xc0154b9f in fork1 ()
#12 0xc015436e in fork ()
#13 0xc0260a59 in syscall2 ()
#14 0xc0255765 in Xint0x80_syscall ()
#15 0x80535f8 in ?? ()
#16 0x482a3a73 in ?? ()
#17 0x80551c9 in ?? ()
#18 0x8065368 in ?? ()
#19 0x80653c9 in ?? ()
#20 0x805e502 in ?? ()
#21 0x805e73d in ?? ()
#22 0x805e9b5 in ?? ()
#23 0x805ee61 in ?? ()
#24 0x805f3a7 in ?? ()
#25 0x804ffd9 in ?? ()

IP points to pmap_insert_entry

---
Fatal trap 12: page fault while in kernel mode
fault virtual address   = 0x8
fault code              = supervisor read, page not present
instruction pointer     = 0x8:0xc021dcbb
stack pointer           = 0x10:0xda803e58
frame pointer           = 0x10:0x0
code segment            = base 0x0, limit 0xfffff, type 0x1b
                        = DPL 0, pres 1, def32 1, gran 1
processor eflags        = interrupt enabled, resume, IOPL = 0
current process         = 1093 (postgres)
interrupt mask          = none
trap number             = 12
panic: page fault

#0  0xc015b4fa in dumpsys ()
#1  0xc015b314 in boot ()
#2  0xc015b69c in poweroff_wait ()
#3  0xc02607f6 in trap_fatal ()
#4  0xc02604b5 in trap_pfault ()
#5  0xc0260087 in trap ()

IP points to ufs_vnoperate

There were also several panics with hanging without complete dump, with at least one double fault (I'm not near the faulty box).
 
Any help is highly appreciated.

One more thing MAY be related with the problem. A week ago clock on that box went backwards about 1 second per minute, and now it is gong backward about one second per hour. 

Disk controller is ADAPTEC 2100S FW Rev. 370F, 1 channel, 256 CCBs, Protocol I2O

-- 
Alex.