It bsod'ed again after serveral weeks of woring fine

You can turn off Driver Verifier. It is not pointing to drivers; but the two BSOD's it has generated are pointing to system drivers and hardware. We will see how your system does with Driver Verifier turned off. The latest dump is inconclusive.

Error code 109, CRITICAL_STRUCTURE_CORRUPTION. Usual causes: Device driver, Breakpoint set with no debugger attached, Hardware (Memory in particular)

There are generally three different causes for this bug check:

• A driver has inadvertently, or deliberately, modified critical kernel code or data. Microsoft Windows Server 2003 with Service Pack 1 (SP1) and later versions of Windows for x64-based computers do not allow the kernel to be patched except through authorized Microsoft-originated hot patches. For more information, see Patching Policy for x64-based Systems.
• A developer attempted to set a normal kernel breakpoint using a kernel debugger that was not attached when the system was started. Normal breakpoints (bp) can only be set if the debugger is attached at start time. Processor breakpoints (ba) can be set at any time.
• A hardware corruption occurred. For example, the kernel code or data could have been stored in memory that failed.

Code:

Windows 7 Kernel Version 7600 MP (8 procs) Free x64
Product: WinNt, suite: TerminalServer SingleUserTS Personal
Built by: 7600.20738.amd64fre.win7_ldr.100618-1621
Machine Name:
Kernel base = 0xfffff800`02c0c000 PsLoadedModuleList = 0xfffff800`02e40eb0
Debug session time: Wed Oct 20 14:01:52.881 2010 (GMT-4)
System Uptime: 0 days 0:24:08.051
Loading Kernel Symbols
...............................................................
................................................................
...................
Loading User Symbols
Loading unloaded module list
.....
*******************************************************************************
*                                                                             *
*                        Bugcheck Analysis                                    *
*                                                                             *
*******************************************************************************

Use !analyze -v to get detailed debugging information.

BugCheck 109, {a3a039d898b675c5, 0, 38df6ea820c39d95, 101}

Probably caused by : Unknown_Image ( ANALYSIS_INCONCLUSIVE )

Followup: MachineOwner
---------

4: kd> !analyze -v
*******************************************************************************
*                                                                             *
*                        Bugcheck Analysis                                    *
*                                                                             *
*******************************************************************************

CRITICAL_STRUCTURE_CORRUPTION (109)
This bugcheck is generated when the kernel detects that critical kernel code or
data have been corrupted. There are generally three causes for a corruption:
1) A driver has inadvertently or deliberately modified critical kernel code
 or data. See Patching Policy for x64-Based Systems: Information for Driver Developers
2) A developer attempted to set a normal kernel breakpoint using a kernel
 debugger that was not attached when the system was booted. Normal breakpoints,
 "bp", can only be set if the debugger is attached at boot time. Hardware
 breakpoints, "ba", can be set at any time.
3) A hardware corruption occurred, e.g. failing RAM holding kernel code or data.
Arguments:
Arg1: a3a039d898b675c5, Reserved
Arg2: 0000000000000000, Reserved
Arg3: 38df6ea820c39d95, Failure type dependent information
Arg4: 0000000000000101, Type of corrupted region, can be
    0 : A generic data region
    1 : Modification of a function or .pdata
    2 : A processor IDT
    3 : A processor GDT
    4 : Type 1 process list corruption
    5 : Type 2 process list corruption
    6 : Debug routine modification
    7 : Critical MSR modification

Debugging Details:
------------------


BUGCHECK_STR:  0x109

CUSTOMER_CRASH_COUNT:  1

DEFAULT_BUCKET_ID:  VERIFIER_ENABLED_VISTA_MINIDUMP

PROCESS_NAME:  System

CURRENT_IRQL:  0

LAST_CONTROL_TRANSFER:  from 0000000000000000 to fffff80002c72580

STACK_TEXT:  
fffff880`033625d8 00000000`00000000 : 00000000`00000109 a3a039d8`98b675c5 00000000`00000000 38df6ea8`20c39d95 : nt!KeBugCheckEx


STACK_COMMAND:  kb

SYMBOL_NAME:  ANALYSIS_INCONCLUSIVE

FOLLOWUP_NAME:  MachineOwner

MODULE_NAME: Unknown_Module

IMAGE_NAME:  Unknown_Image

DEBUG_FLR_IMAGE_TIMESTAMP:  0

BUCKET_ID:  BAD_STACK

Followup: MachineOwner
---------

Obviously, the dump points to hardware. I suggest you test your CPU and RAM with Prime. Read and follow the instructions in this tutorial:

https://www.sevenforums.com/tutorials...t-prime95.html

Run 3 separate tests, one on each of the setting (Blend, Small FFTs, Large FFTs). Post back with the results.