i have the thunderbolt, but i don't use the app you're talking about
i can honestly say i hate the thunderbolt though. mine sends text messages to random people. i'll have the message typed into the conversation with one person, hit send, and watch as it switches to another conversation and then sends it. also the battery life lasts like 2 hours, the mobile wifi now costs money, and the service sucks for the most part as well. i've had to restart the phone multiple times when it said i had no service, and after restarting it would have full bars. it pisses me off. /end rant
that being said, it might just be a glitch with your phone.
thankfully i've found an app that mimics the mobile wifi, and i also found out how to play pokemon on mine. pokemon is the tits