I've noticed that TMReachabilityCallback is called with flags == 0 if there is a existing internet connection via wifi on os x mavericks, i think you should add a workaround like this:
-(BOOL)isReachableWithFlags:(SCNetworkReachabilityFlags)flags
{
if (flags == 0)
return YES;
Maybe there is a better solution, but TMReachabilityCallback is called only once