Are you trying to use your ViaTalk SIP credentials in the OBi110 to replace an ATA you have been using with ViaTalk, or are you connecting the OBi110's LINE port to the ViaTalk ATA's PHONE port? If it's the latter, it should be straightforward.
If you have your ViaTalk SIP credentials and are trying to replace the ViaTalk ATA, try the following configuration (this assumes you have Google Voice on SP1 and ViaTalk on SP2):
System Management -> Device Update -> Reset Configuration
System Management -> Network Settings -> LocalTimeZone : [your local time zone]
System Management -> Auto Provisioning -> Method : Disabled
Service Providers -> ITSP Profile A -> General -> SignalingProtocol : Google Voice
Voice Services -> SP1 Service -> AuthUserName : [your Google Voice username]
Voice Services -> SP1 Service -> AuthPassword : [your Google Voice password]
Service Providers -> ITSP Profile B -> SIP -> ProxyServer : [the ViaTalk proxy server name or IP address]
Voice Services -> SP2 Service -> X_ServProvProfile : B
Voice Services -> SP2 Service -> AuthUserName : [your ViaTalk username]
Voice Services -> SP2 Service -> AuthPassword : [your ViaTalk password]
Physical Interfaces -> Phone Port -> PrimaryLine : [your choice]