aswTdi.sys frequently Crashing Computer

Hello,
I am running avast! Internet Security, program version 8.0.1489 on windows 7 Ultimate 64-bit Service Pack 1.
At least once a week my system is crashing to blue screen reporting aswTdi.sys file crashed.

Here is a couple of examples from WhoCrashed

On Tue 7/9/2013 12:23:17 PM GMT your computer crashed
crash dump file: C:\Windows\Minidump\070913-30076-01.dmp
This was probably caused by the following module: aswtdi.sys (aswTdi+0x45F5)
Bugcheck code: 0x3B (0xC0000005, 0xFFFFF88002C045F5, 0xFFFFF88006358D80, 0x0)
Error: SYSTEM_SERVICE_EXCEPTION
file path: C:\Windows\system32\drivers\aswtdi.sys
product: avast! Antivirus
company: AVAST Software
description: avast! TDI Filter Driver
Bug check description: This indicates that an exception happened while executing a routine that transitions from non-privileged code to privileged code.
This appears to be a typical software driver bug and is not likely to be caused by a hardware problem.
A third party driver was identified as the probable root cause of this system error. It is suggested you look for an update for the following driver: aswtdi.sys (avast! TDI Filter Driver, AVAST Software).
Google query: AVAST Software SYSTEM_SERVICE_EXCEPTION

On Wed 7/3/2013 8:40:45 AM GMT your computer crashed
crash dump file: C:\Windows\Minidump\070313-24414-01.dmp
This was probably caused by the following module: aswtdi.sys (aswTdi+0x45F5)
Bugcheck code: 0x3B (0xC0000005, 0xFFFFF88002DE75F5, 0xFFFFF8800BDF8A80, 0x0)
Error: SYSTEM_SERVICE_EXCEPTION
file path: C:\Windows\system32\drivers\aswtdi.sys
product: avast! Antivirus
company: AVAST Software
description: avast! TDI Filter Driver
Bug check description: This indicates that an exception happened while executing a routine that transitions from non-privileged code to privileged code.
This appears to be a typical software driver bug and is not likely to be caused by a hardware problem.
A third party driver was identified as the probable root cause of this system error. It is suggested you look for an update for the following driver: aswtdi.sys (avast! TDI Filter Driver, AVAST Software).
Google query: AVAST Software SYSTEM_SERVICE_EXCEPTION

I am only running the native windows firewall and Windows Defender. No other software for virus protection or firewall.

Does anyone have any reasons as to what could be causing this?
Thanks!

Strange. See this
I would say disable the windows firewall and see if the problem is still there.

Thanks for your reply Eddy. I will have to try that.