Avast 6.0 free crashed my system!! help

[MaxReed]

I tried to see the settings of avast on the second computer and I saw that are different from the one that crashes with the pen drive with the file autorun.inf.
The differences are in "File system protection" advanced settings.

The settings on first computer are:                               The settings on second computer are:
-scanning during opening/analize all files  YES                       NO
-scanning during writing/analize all files  YES                       NO
-archives of files/all the packers  YES                                  NO
-sensibility/heuristics sensibility/HIGH  YES                      NO / NORMAL
-sensibility/sensibility/makes tests on entire files  YES                       NO
-sensibility/sensibility/make scan for PUP  YES                       NO

So,I decided to change the settings on the second PC to make it how the first.I tried to insert the pen drive with the autorun.inf and...also the second crashed.
I tried the same operation on my laptop (ASUS N61Jv with windows7 pro).Also the laptop go in crash.
I'm thinking that the problem can't be of the USB hub becouse three hub corrupted in the same time is improbably.
Moreover the same problem occurs with SD card on laptop.

Well, What is the real problem?

Help please! I'm very confused

[MaxReed]

The problem occurs on all pen drive I have and all SD and on all PC if I set avast in the same way (that i consider the most secure).

I'm sorry I wanted to summarize and combine everything I wrote in only one post

[MaxReed]

I think I solved the problem!
I formatted the pen-drive and I changed the file system into FAT32 from NTFS.
Now the problem seems solved...hopefully good

Thanks to all for the help given