problems using ntfssecurity CMDLETS

Hi,

I am using NTFSSecurity CMDLets to set permissions for AD groups to NTFS filesystem:

http://gallery.technet.microsoft.com/scriptcenter/1abd77a5-9c0b-4a2b-acef-90dbb2b84e85

The Script is working ok for some groups, but not for some others.

Groups that contain ~ and/or ! do not work. I get an error: "Some or all identity references could not be translated."

When I use Get-Adgroup with the same problematic group, I do get a normal result.

Any ideas how to fix this? I have a lot of groups with ! and ~.

Main piece of script:

Get-Item $folder | Add-Ace -Account $Principal -AccessRights $Right -Inheritanceflag $inheritanceflag -Propagationflag $propagationflag

The variables come from a .csv that contain the information needed. The $Principal Variable contains the groupname.

Any help would be greatly appreciated.