Both crashes\bsod point to EtronXHCI.sys
your Etron USB 3.0 Extensible Host Controller Driver.
We have a little info about this driver. Etron Technology Inc.
I suggest for now that you disable the EtronXHCI.sys driver.
This will show whether it is really the cause or is just being blamed. Go to C:\Windows\System32\drivers and rename it by changing the .sys extension to something else like .old. Be aware this will also "break" the software that uses this driver.
Remove avast from your system.
Download and install and Microsoft Security Essentials
with windows firewall enable.
and post back.