Every time I try to open Documents from the Start menu...

It crashes and I receive the "Windows Explorer has stopped working" error.
It started ever since I upgraded my [COLOR=green !important][FONT=inherit !important][COLOR=green !important][FONT=inherit !important]antivirus[/FONT][/FONT][/COLOR][/COLOR] (Bitdefender). So I reverted back to the older version, and I still keep receiving the same error and it's just annoying!
Can anyone pinpoint the problem and tell me what I should do? I've tried discussing this with Microsoft and a couple other forum sites, and so far, no one has been able to help me.

Problem signature:
Problem Event Name: APPCRASH
[COLOR=green !important][FONT=inherit !important][COLOR=green !important][FONT=inherit !important]Application[/FONT][/FONT][/COLOR][/COLOR] Name: Explorer.EXE
Application Version: 6.0.6002.18005
Application Timestamp: 49e01da5
Fault Module Name: windowscodecsext.dll
Fault Module Version: 7.0.6002.18107
Fault Module Timestamp: 4abc25ca
Exception Code: c0000005
Exception Offset: 00005cd1
OS Version: 6.0.6002.2.2.0.256.1
Locale ID: 1033
Additional Information 1: 40d4
Additional Information 2: 4062ad41ec8067256aa4c5e2b56d3c79
Additional Information 3: 40d4
Additional Information 4: 4062ad41ec8067256aa4c5e2b56d3c79


Also, I keep getting that same error every time I try to search from my Computer as well...

Problem signature:
Problem Event Name: APPCRASH
Application Name: explorer.exe
Application Version: 6.0.6002.18005
Application Timestamp: 49e01da5
Fault Module Name: windowscodecsext.dll
Fault Module Version: 7.0.6002.18107
Fault Module Timestamp: 4abc25ca
Exception Code: c0000005
Exception Offset: 00006bff
OS Version: 6.0.6002.2.2.0.256.1
Locale ID: 1033
Additional Information 1: fd00
Additional Information 2: ea6f5fe8924aaa756324d57f87834160
Additional Information 3: fd00
Additional Information 4: ea6f5fe8924aaa756324d57f87834160


Here's my info:

OS Version: Microsoft® Windows Vista™ Ultimate, [COLOR=green !important][FONT=inherit !important][COLOR=green !important][FONT=inherit !important]Service [/FONT][COLOR=green !important][FONT=inherit !important]Pack[/FONT][/COLOR][/FONT][/COLOR][/COLOR] 2, 32 bit
Processor: Intel(R) Core(TM)2 Duo CPU E6850 @ 3.00GHz, x64 Family 6 Model 15 Stepping 11
Processor Count: 2
RAM: 3326 Mb
[COLOR=green !important][FONT=inherit !important][COLOR=green !important][FONT=inherit !important]Graphics [/FONT][COLOR=green !important][FONT=inherit !important]Card[/FONT][/COLOR][/FONT][/COLOR][/COLOR]: ATI Radeon HD 2600 PRO, 512 Mb
Hard Drives: C: Total - 476937 MB, Free - 85190 MB;
[COLOR=green !important][FONT=inherit !important][COLOR=green !important][FONT=inherit !important]Motherboard[/FONT][/FONT][/COLOR][/COLOR]: MICRO-STAR INTERNATIONAL CO.,LTD, MS-7345
Antivirus: BitDefender Antivirus, Updated and Enabled

Welcome
Make a full anti virus scan
Download and make a full scan with malwarebytes
If both are negative, follow the clean boot procedure and hopefully find the cause
Troubleshoot Application Conflicts by Performing a Clean Startup - Windows 7 Forums

I ran both BitDefender and Malwarebytes. They were both clear.
And I did a clean boot, which didn't help either. I have been led to believe that it has something to do with windowscodecsext.dll. Any suggestions that could help me at this point would be greatly appreciated.

That's probably what's causing it - but we don't know the mechanism behind it.

Please provide these reports even though you're not experiencing BSOD's: http://www.vistax64.com/crashes-debugging/282419-blue-screen-death-bsod-posting-instructions.html

See if creating a new User account reproduces the problem - it may be your User profile is corrupted.