Continuity mistake: During the surgery, when they attempt to remove the Goa'uld, they start a timer. The timer starts at 00:00:00, then it blacks out (obviously, you don't want to be bored by major neck-surgery), and then the timer is at 01:19:49. However, seconds later (after Carter and Daniel's conversation), look at the timer in the background, it reads 00:23:46.
Plot hole: Huge plot error: Apophis and Clorell (Skara) should not have survived the explosion in Season 2, Episode 1 (when they attack Earth with two ships). In "Family" they explain that Apophis and Clorell survived by escaping through the stargate aboard Clorell's ship moments after Daniel Jackson did the same. However, when Daniel Jackson escapes through it, Apophis and Clorell are not even on the right ship, and there is 1 second left on the C4 timer when Daniel escapes. They actually show Daniel Jackson escape, and then cut to Apophis and Clorell still aboard their ship. So apparently, Apophis was able to "ring" from his ship over to Clorell's ship, make it to the stargate room, dial an address, and escape through the stargate all within literally 1 second. Is this guy related to The Flash?
Continuity mistake: Daniel's interaction is inconsistent across the episode. Initially, Daniel emerges through the Stargate with no ripples in the event horizon or audible noise. Then he walks down the metal ramp making noise with each footfall. Later in the episode he returns through the Stargate with an audible noise and ripples in the event horizon. He remained "out of phase" for the entire segment of the episode.
Continuity mistake: Jacob Carter repeatedly mentions blending with Selmak 4 years ago, placing it in Series 4 (each season constitutes a year - when Carter leaves the SGC to join Atlantis at the conclusion of season 10, she talks to Teal'c about how they have spent 10 years together). However the blending occurred in Series 2 (6 years ago).
Plot hole: The team are finding out who could have stolen the weather device from Madrona and find an energy spike at the same time SG2 are on a mission. "But SG2's mission is galaxies away from Madrona" Says Teal'c. At this time the only missions the teams could go on was in our own galaxy and couldn't be galaxies away.
Factual error: The escort for Colonel O'Neill is wearing both Major and Staff Sergeant rank insignia. Probably what the writers thought was a "Sergeant Major", which does not exist in the Air Force. Major is a commissioned officer, sergeants are non-commissioned officers.