I found that after upgrade PowerShell to version 3 you may discover the following error on startup:
Attempting to perform the InitializeDefaultDrives operation on the 'FileSystem' provider failed.
The most probably this is caused by disconnected network drive in My computer
You can try to disconnect unused drives.
You can also try to fix it by setting some registry key using the following PowerShell script:
Set-ItemProperty -Path Registry::HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Policies\System -Name EnableLinkedConnection -Value 1 -Type DWord