Please try running icomancer as administrator and then setting the icon to the folder. If after this, the problem persists, please let me know.

System.NotSupportedException: The given path's format is not supported.
at System.Security.Permissions.FileIOPermission.EmulateFileIOPermissionChecks(String fullPath)
at System.Security.Permissions.FileIOPermission.QuickDemand(FileIOPermissionAccess access, String fullPath, Boolean checkForDuplicates, Boolean needFullPath)
at System.IO.FileInfo.Init(String fileName, Boolean checkHost)
at System.IO.FileInfo..ctor(String fileName)
at Icomancer.Functions.ExtractIconToFile(String SourceIconPath) in H:\Icomancer\Icomancer\Functions.vb:line 1392
at Icomancer.frmImbuer.LocalCollectionSelector_PathChanged(String changedPathName, String changedFullPath) in H:\Icomancer\Icomancer\frmImbuer.vb:line 590
at Icomancer.uctlFolderTree.Tree_AfterSelect(Object sender, TreeViewEventArgs e) in H:\Icomancer\Icomancer\uctlFolderTree.vb:line 80
at System.Windows.Forms.TreeView.OnAfterSelect(TreeViewEventArgs e)
at System.Windows.Forms.TreeView.TvnSelected(NMTREEVIEW* nmtv)
at System.Windows.Forms.TreeView.WmNotify(Message& m)
at System.Windows.Forms.TreeView.WndProc(Message& m)
at System.Windows.Forms.Control.ControlNativeWindow.OnMessage(Message& m)
at System.Windows.Forms.Control.ControlNativeWindow.WndProc(Message& m)
at System.Windows.Forms.NativeWindow.Callback(IntPtr hWnd, Int32 msg, IntPtr wparam, IntPtr lparam)

Please take a screen shot of this and send it to icomancer_support@lavasoftworks.com so we can figure out how to fix it.