Since the latest update of the PlayBook has brought some new great features, unfortunately it came at a slight cost. You cannot do wifi sharing. But not a problem, because there is a solution. Simply follow these steps to get it working.
1. You’ll need the IP address of your PlayBook:
Open the PlayBook’s settings by tapping the Gear icon in the upper right of the Status Ribbon
Select the About tab, and then select Network from the drop-down menu
You want the IPv4 address, which will probably be something like 192.168.x.x
2. Windows XP. Use the Windows Key-R combination to open the run menu. Type \\192.xxx.x.x That’s backslash-backslash your-playbooks-ip For example, I would type \\192.168.1.2
Windows Vista, Windows 7: Same thing, but you can also type that in the bar at the bottom of the Start menu
Mac: “[S]elect Go -> Connect to Server… and type smb://127.1.1.1 (where 127.1.1.1 should be replaced with the actual IP address of the BlackBerry PlayBook)”
Did it work for you?