iscsitarget locks up and kernel BUG reported in syslog

Binary package hint: iscsitarget

This is happening regularly, don't know why, google wasn't any help. Maybe someone smarter then I can take a crack at this.

Oct 8 10:28:19 ubuntu kernel: [ 2707.646687] BUG at /usr/src/iscsitarget-0.4.15/kernel/iscsi.c:689 assert(tio->pvec[idx])
Oct 8 10:28:19 ubuntu kernel: [ 2707.646795] [<f906e05f>] cmnd_recv_pdu+0x19f/0x1d0 [iscsi_trgt]
Oct 8 10:28:19 ubuntu kernel: [ 2707.646813] [<f906fa77>] cmnd_rx_start+0x707/0xa90 [iscsi_trgt]
Oct 8 10:28:19 ubuntu kernel: [ 2707.646824] [_spin_lock_bh+8/32] _spin_lock_bh+0x8/0x20
Oct 8 10:28:19 ubuntu kernel: [ 2707.646832] [release_sock+18/176] release_sock+0x12/0xb0
Oct 8 10:28:19 ubuntu kernel: [ 2707.646839] [tcp_ioctl+254/384] tcp_ioctl+0xfe/0x180
Oct 8 10:28:19 ubuntu kernel: [ 2707.646845] [tcp_ioctl+0/384] tcp_ioctl+0x0/0x180
Oct 8 10:28:19 ubuntu kernel: [ 2707.646851] [<f90714c4>] istd+0xea4/0x1060 [iscsi_trgt]
Oct 8 10:28:19 ubuntu kernel: [ 2707.646863] [__activate_task+33/64] __activate_task+0x21/0x40
Oct 8 10:28:19 ubuntu kernel: [ 2707.646875] [tcp_sendpage+0/1552] tcp_sendpage+0x0/0x610
Oct 8 10:28:19 ubuntu kernel: [ 2707.646884] [complete+64/96] complete+0x40/0x60
Oct 8 10:28:19 ubuntu kernel: [ 2707.646891] [<f9070620>] istd+0x0/0x1060 [iscsi_trgt]
Oct 8 10:28:19 ubuntu kernel: [ 2707.646901] [kthread+186/240] kthread+0xba/0xf0
Oct 8 10:28:19 ubuntu kernel: [ 2707.646908] [kthread+0/240] kthread+0x0/0xf0
Oct 8 10:28:19 ubuntu kernel: [ 2707.646914] [kernel_thread_helper+7/20] kernel_thread_helper+0x7/0x14
Oct 8 10:28:19 ubuntu kernel: [ 2707.646921] =======================
Oct 8 10:28:19 ubuntu kernel: [ 2707.646931] ------------[ cut here ]------------

System is Ubuntu server 64 bit.