Since Snow Leopard (and also Lion), there is an issue with the Group SMS feature of SMS Mac.
In Snow Leopard and Lion, Apple has disabled support for Contextual Menu Items (CMI) plug-ins in the Address Book and hence the Control-Click or Right-Click (using the mouse) command through plug-ins.
The Group SMS feature of SMS Mac is implemented as a CMI command (like Send SMS to "group name"
) in the popup menu, which you get when you Control-Click or Right-Click on a group name (left column) in the Address Book. So this feature does not work anymore in Snow Leopard. That is, the command just does not show up anymore in the contextual menu.
Fortunately, there is a work-around. In the Finder, select the Address Book application, and choose the command Get Info (Cmd-I) from the File menu. In the Get Info Window, enable the option to run the Address Book in 32-bit mode.
When you now relaunch the Address Book, the CMI plug-in will again work and you'll have the Send SMS command again for groups.
By the way, you must upgrade to SMS Mac 2.5 for all this to work on Lion and Snow Leopard.