Powershell Bug in copy/move/rename when filename contains [square bracket characters]?

Please pardon a noob question, but I've been completely baffled by this one.

I have a "depositor" directory where user-submitted files arrive, and have no control over the incoming file names.

I created a parser in PS which quite successfully moves files (based on file name content) to an appropriate destination.

This works fine EXCEPT when a filename contains either "[" or "]".

Here is the "rename" pre-processor, which fails to actually rename a file containing either of the pesky bracket characters:

 cd $folderpath
 foreach ($i in get-childitem $folderpath) {   
     if ($i.mode.substring(0,1) -ne “d”) {
        $name = $i.name.replace("[","_")
        $name = $name.replace("]","_")
        Write-Host $i -foregroundcolor “blue”       
        Write-Host $name -foregroundcolor “green”  


        Rename-Item $i $name 

     }
 }

This also fails for ren, copy, move and their cmdlet equivalents

Any insight you might be able to provide would be most welcome.

Thanks in advance . . .