Debug a Volume filter driver on Windows Storage Server 2008

I’m developing a volume class upperfilter driver. this driver works well on xp,but will crash system in boot time on windows storage server 2008.
I use WinDBG+VirtualBox to debug.
when restart the target, it is stoped with a black screen. but host wait the connection always.So I can not debug the target.

I want to debug the target,how to break it and let host connect to target?

additional information:
I used VirtualKD. It works very well if I do not load my driver in target.But when I set my driver start at boot time, the target halted, but windbg not breaking in.

Microsoft (R) Windows Debugger Version 6.12.0002.633 X86
Copyright (c) Microsoft Corporation. All rights reserved.

Opened \.\pipe\kd_Windows_Storage_Server_2008-X64
Waiting to reconnect…
Connected to Windows 7 7601 x64 target at (Fri Apr 27 16:59:32.812 2012 (UTC + 8:00)), ptr64 TRUE
Kernel Debugger connection established. (Initial Breakpoint requested)
Symbol search path is: srv*d:\symbols*
Executable search path is:
Windows 7 Kernel Version 7601 MP (1 procs) Free x64
Built by: 7601.17514.amd64fre.win7sp1_rtm.101119-1850
Machine Name:
Kernel base = 0xfffff8000160c000 PsLoadedModuleList = 0xfffff80001851e90
System Uptime: not available
Break instruction exception - code 80000003 (first chance)
* *
* You are seeing this message because you pressed either *
* CTRL+C (if you run kd.exe) or, *
* CTRL+BREAK (if you run WinDBG), *
* on your debugger machine’s keyboard. *
* *
* *
* If you did not intend to break into the debugger, press the “g” key, then *
* press the “Enter” key now. This message might immediately reappear. If it *
* does, press “g” and “Enter” again. *
* *
fffff80001684490 cc int 3 kd\> lm start end module name fffff800014b4000 fffff800014de000 kdbazis (deferred) fffff8000160c000 fffff80001bf6000 nt (pdb symbols) d:\symbols\ntkrnlmp.pdb\3844DBB920174967BE7AA4A2C20430FA2\ntkrnlmp.pdb fffff80001bf6000 fffff80001c3f000 hal (deferred) fffff88000c00000 fffff88000c5c000 volmgrx (deferred) fffff88000c5c000 fffff88000c76000 mountmgr (deferred) fffff88000c76000 fffff88000c7f000 atapi (deferred) fffff88000c7f000 fffff88000ca9000 ataport (deferred) fffff88000ca9000 fffff88000cb4000 msahci (deferred) fffff88000cbc000 fffff88000d0b000 mcupdate_GenuineIntel (deferred) fffff88000d0b000 fffff88000d1f000 PSHED (deferred) fffff88000d1f000 fffff88000d7d000 CLFS (deferred) fffff88000d7d000 fffff88000db0000 pci (deferred) fffff88000db0000 fffff88000dc5000 volmgr (deferred) fffff88000dc5000 fffff88000dd0000 amdxata (deferred) fffff88000e00000 fffff88000ea4000 Wdf01000 (deferred) fffff88000ea4000 fffff88000ead000 compbatt (deferred) fffff88000ead000 fffff88000eb9000 BATTC (deferred) fffff88000eb9000 fffff88000ec9000 PCIIDEX (deferred) fffff88000ec9000 fffff88000f89000 CI (deferred) fffff88000f89000 fffff88000fa4000 sacdrv (deferred) fffff88000fa4000 fffff88000ffb000 ACPI (deferred) fffff88001000000 fffff88001060000 NETIO (deferred) fffff88001063000 fffff88001156000 NDIS (deferred) fffff88001156000 fffff880011b4000 msrpc (deferred) fffff880011b4000 fffff880011c3000 WDFLDR (deferred) fffff880011c3000 fffff880011cc000 WMILIB (deferred) fffff880011cc000 fffff880011d6000 msisadrv (deferred) fffff880011d6000 fffff880011e3000 vdrvroot (deferred) fffff880011e3000 fffff880011f8000 partmgr (deferred) fffff880011f8000 fffff88001200000 intelide (deferred) fffff880012cb000 fffff88001317000 fltmgr (deferred) fffff88001317000 fffff88001389000 cng (deferred) fffff88001389000 fffff8800139a000 pcw (deferred) fffff8800139a000 fffff880013c5000 ksecpkg (deferred) fffff88001400000 fffff8800141b000 ksecdd (deferred) fffff8800141b000 fffff88001445000 VBoxGuest (deferred) fffff88001445000 fffff8800144f000 Fs_Rec (deferred) fffff88001452000 fffff880015f5000 Ntfs (deferred) fffff8800162d000 fffff88001831000 tcpip (deferred) fffff88001831000 fffff8800187b000 fwpkclnt (deferred) fffff8800187b000 fffff8800188b000 vmstorfl (deferred) fffff8800188b000 fffff880018d7000 volsnap (deferred) fffff880018d7000 fffff880018df000 spldr (deferred) fffff880018df000 fffff880018f1000 mup (deferred) fffff880018f1000 fffff880018fa000 hwpolicy (deferred) fffff880018fa000 fffff88001910000 disk (deferred) fffff88001910000 fffff880`01940000 CLASSPNP (deferred)

when restart OS, not load my driver, I can break in the target at the boot time.