Character mistake: Previous episodes have established this story arc to be occurring in the year 2154. Yet here, when T'Pol records her log, she cites the date as 2152. (00:32:00)
Character mistake: In Engineering, Trip calls Commander Kelby "Lieutenant."
Other mistake: Two Borg are discovered North of the Arctic Circle. One is covered in ice, the other encased in ice. Carbon dating shows the wreckage to be over 100 years old (to tie it in with Star Trek: First Contact). The Borg are inactive and unable to repair themselves until they are "defrosted". The temperature above the Arctic Circle doesn't usually drop below -100°F. The Borg have been shown to work very well in the vacuum of space which is 3-4K (roughly -454°F). If they can survive that, even being frozen in a solid block of ice would not slow them down. The nanites have to be in their "blood" and operate at the cellular level. That cannot be damaged by re-entry and the crash.
Subcommander T'Pol: The Captain's behavior is becoming increasingly illogical, even for a human.
Trivia: A film reference to Star Trek: First Contact: Archer says something about a group of cybernetic creatures (The Borg), that tried to stop Cochrane from launching his mission into space that was stopped by a group of humanoids, that were also from the future (USS Enterprise NCC 1701-E).
Question: Is the captain's dog still alive?
Answer: Yes. Porthos survives this episode, although many a viewers' sanity and the show's ratings were not so lucky.