Please upgrade to the latest version?
There are two ways to whitelist a member.
One is to assign them a new special membergroup that has "Bad Behavior Whitelist Group" enabled in admin/Permissions/General Permissions. The downside with this method is that it uses the ip addresses stored in SMF. This means that if their address changes they can fail.
The second, more difficult and, more fail proof method is to edit the BB "whitelist.ini" file. Here you can add their hosts ip range in CIDR format to the file. Click the link for help