Likely a basic issue. GV voicemail answers in 25 seconds, about 5 rings. If you're forwarding to your cell all the time, and it's off or in use, then its voicemail will answer. Two options, both under Advanced Options in GV. First, you can setup GV as the voicemail provider on your cell. And you can even tell it to ring other phones, i.e. the Gtalk which rings the OBi, before leaving a voicemail. Or, uncheck the forwarding box on GV, or setup a schedule for when to forward to it.