In Stargate Universe, they recently attempted to dial home to Earth by using the power of star, creating the wormhole from within the star.
The very next episode, they mentioned that solar flares can cause the wormhole to bounce back and travel through time.
So, wouldn't dialing from within a star contain a somewhat heightened danger of accidental time travel? OK, so solar activity is somewhat unpredictable, and presumably varies from star-to-star, so the risk might be somewhat limited.
But still, it seems like the idea of creating a wormhole from within a star seems to be a bit... dangerous.
To be fair, Dr. Rush does complain that attempting to dial from within the star would be dangerous - except no one's quite sure that he's telling the truth, and he doesn't state exactly what the danger is.