Windows 7: Little problem with av

Ok will try to explain my problem...
A few days ago i installed win 7 build 7600 32bit and i had few problems but i fix it my self or i founded solutions on this forum and with google.
I used xp long time and sudenly i wanted to try Windows 7...on xp i used some stupid av because without him i couldnt run os normaly there were crashes,programs wont start etc.
I used Symantec.AntiVirus.Corporate.Edition.v10.1.7000.7 and that fixed all problems and i used xp normally but without him couldnt use it normaly.
Now on Windows 7 its not possible to use it...i installed Microsoft Security Essentials and now again i have same problems which i have on xp...msn when login i got error same thing with mozilla firefox 3 and with few other programs.Does anyone know what should i do?How to fix that problem? or should i install xp again
Edit:Here are some ss,hope will help to understand
ImageShack Gallery
Problem signature:
Problem Event Name: APPCRASH
Application Name: msnmsgr.exe
Application Version: 8.5.1302.1018
Application Timestamp: 4717a53b
Fault Module Name: kernel32.dll
Fault Module Version: 6.1.7600.16385
Fault Module Timestamp: 4a5bdaad
Exception Code: c0000005
Exception Offset: 00034143
OS Version: 6.1.7600.2.0.0.256.1
Locale ID: 1033

Additional information about the problem:
LCID: 1033

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Sry for bad english i'm from Serbia!hope will understand someone