Hi, My name is Eric Moyers. I am a Network Support Engineer in the Cisco Small Business Support Center.
Are you trying to check the box before you create the tunnel settings? Try creating the tunnel and saving it, then check the enable button. If that does not work please call into the Support Center for additional support.
Cisco Small Business Support contacts:
http://www.cisco.com/go/sbsc
Eric Moyers
Cisco Network Support Engineer
CCNA, CCNA-Wireless
1-866-606-1866