Keyboard input causing App freeze

I am having this weird problem.
When i try to use keyboard, whatever is open in front of me hangs. Be it the file explorer, start menu, office etc... And Description says " A problem caused this program to stop interacting with windows".
This problem is random and occurs few times every day. When i restart the system, it becomes ok for a while but then again the same.
No recent change in drivers or windows copy. Using the exact same copy since 3 years and no problem. Have reinstalled 3 times and still end up with same problem.
Problem doesn't go away even after fully updating the windows.

I have tried running sfc /scannow but it didn't find anything. Though system ran fine all day after running this command, but next day the same.
Tried uninstalling Keyboard/USB root hub drivers and restart but no result again.

And yeah, on windows 8.1 everything runs fine and stable. Problem is only in Windows 7.

A shot for example

As long as i don't use keyboard, everything works nice and stable.
A quick googling shows this ApphangB1 issue is faced by many people. I wonder why i am facing it all of a sudden after so many years of smooth sailing with 7.

A full report from hang when tried to type something in start menu.

Description:
A problem caused this program to stop interacting with Windows.

Problem signature:
Problem Event Name: AppHangB1
Application Name: explorer.exe
Application Version: 6.1.7601.17567
Application Timestamp: 4d672ee4
Hang Signature: 1464
Hang Type: 0
OS Version: 6.1.7601.2.1.0.256.1
Locale ID: 1033
Additional Hang Signature 1: 1464218bd39880a5f084580160e63a27
Additional Hang Signature 2: 0fd5
Additional Hang Signature 3: 0fd503679453becbed7675dae837edbf
Additional Hang Signature 4: 1464
Additional Hang Signature 5: 1464218bd39880a5f084580160e63a27
Additional Hang Signature 6: 0fd5
Additional Hang Signature 7: 0fd503679453becbed7675dae837edbf

No suggestions??

Ok, helping myself.... :)

Googling the issue suggested that this is mainly due to compromised system files. Now i could understand that but why happening on fresh installation?
Only cause could be problem in storage disk. My SSD endured quite a bit of abuse last month and perhaps trim couldn't keep up with it. So i went ahead and secure erased the whole drive, bringing it back to box packed condition.
Used Parted Magic for this purpose.

Time for a fresh reinstall...
Hope installation remains intact now.

Still same.
System worked fine for a day and next day same hang on keyboard input.

I guess i'll just stick to 8.1 then.

SSD health seems good.