panic: bremfree: buffer 0xdc6ff768 not on a queue.

A dual CPU machine running 6.0 from a couple of weeks ago panicked
overnight with:

panic: bremfree: buffer 0xdc6ff768 not on a queue.
cpuid = 1
KDB: enter: panic
[thread pid 26507 tid 100945 ]
Stopped at      kdb_enter+0x30: leave
db> wh
Tracing pid 26507 tid 100945 td 0xc6eda730
kdb_enter(c06f5a0f,1,c06fce5f,ef4a5a68,c6eda730) at kdb_enter+0x30
panic(c06fce5f,dc6ff768,2090022,ef4a5aa8,c0569188) at panic+0x14e
bremfree(dc6ff768,2090022,c4544450,c6eda730,0) at bremfree+0x5d
getblk(c4544450,b,0,4000,0) at getblk+0x1a8
cluster_read(c4544450,32ea8,0,b,0) at cluster_read+0x108
ffs_read(ef4a5c0c,c0730880,c4544450,c663d048,ef4a5c58) at ffs_read+0x2e0
VOP_READ_APV(c07391e0,ef4a5c0c,c6eda730,36f,0) at VOP_READ_APV+0xbc
vn_read(c663d048,ef4a5c80,c9e26d00,0,c6eda730) at vn_read+0x1e7
dofileread(c6eda730,c663d048,3,8064000,8000) at dofileread+0xcc
read(c6eda730,ef4a5d14,c,16,3) at read+0x6b
syscall(805002f,2f,bfbf002f,8000,1000) at syscall+0x2a0
Xint0x80_syscall() at Xint0x80_syscall+0x1f
--- syscall (3, FreeBSD ELF32, read), eip = 0x280f8b3f, esp = 0xbfbfb7cc, ebp = 0xbfbfb858 ---
db>

Is this problem already fixed?

Kris