Audio problem: When Jerry uses the elevator, the voice of the computer reads out the floors as "twenty-third floor, fourth floor, fifth floor" etc, missing out the "twenty-" prefix until the 29th floor. The DVD subtitles list these numbers with their prefix, so this was not intentional. (00:21:10)
Never Again - S4-E13
Visible crew/equipment: When Ed turns to go into the office, you see the reflection of the boom mike on the glass window. (00:05:30)
Revealing mistake: When the doctor examine Ronnie's "corpse" in the morgue, he pulls out the stake. It is quite obvious that he's struggling with a wooden stake that is placed on the actor's side, not through his chest. Moreover, the camera pans up and you can briefly see Ronnie's unharmed chest.
Fresh Bones - S2-E15
Visible crew/equipment: When Mulder chases Chester on the pier, the camera's shadow can be seen as it circles around him. (00:25:25)
Continuity mistake: When Skinner walks into the cafe (the time he gets shot) another man is just walking out, leaving a table with a used glass and coffee cup. The waitress is in the back, getting Skinner a cup of coffee (she couldn't have cleaned the other table yet), but when we look over Skinner's shoulder you can see that the other table is cleared and has a clean coffee cup (turned upside down) on it.
Red Museum - S2-E10
Continuity mistake: When the old man shows Mulder the two guys, the one that is not Deep Throat's murderer, from a distant angle his shirt is completely red. In the close-up he has a red and a bit green shirt.

Continuity mistake: When the cup falls over when Lauren wants to see Mr. Dorlund, the box of tissues disappears in the last shot. (00:08:20)

Continuity mistake: When Scully is in her room after the autopsy, we see the x-ray attached to her lamp. When we first see it, we can see the letters LD on it, yet when the shot changes back to the x-ray after Mulder has gone, we can only see I, presumably the other x-ray is now overlapping it. (00:15:20 - 00:16:10)

Continuity mistake: When Mulder and Scully are driving after their plane lands, we see at one point that Mulder has his left hand on the wheel and he is eating a sunflower seed with his right, yet when the shot changes he's driving with his right hand and eating with his left. (00:09:45)

Factual error: The flag in Skinner's office is hung upside-down. (00:28:00)
Visible crew/equipment: When Brad is showing Mulder and Scully the video tape in his house, you can see the crew reflected off the TV screen. (00:12:50)
Factual error: The Arecibo Radio Telescope is abandoned when Mulder goes there. However, after SETI was cancelled, the telescope was still used for other things. (00:16:50)

Other mistake: Mulder pulls in to park in front of a red car. The front plate on both Mulder's and the red car is the same: 5S2 706. (00:27:37)
Continuity mistake: During the conversation with Scully regarding Wayne Weinsider, Mulder says "I don't know why. I'm not a psychologist", which must be a big surprise for all viewers, to say the least. Mulder graduated from Oxford University with a Bachelor of Arts degree in Psychology (e.g. "Dreamland II") and he worked for some time as a profiler for the FBI (e.g. "Young at Heart"). (00:32:25)

Continuity mistake: In the close-up shot of Mulder just before he shoots Barnett, his black ear piece disappears. (00:42:15)
Continuity mistake: It seemed strange that Mulder was surprised not to find the Arthur Dales he knew at his apartment, when in "Agua Mala," he learned that Dales had moved to Florida. (00:08:30)
Answer: He was being facetious. He doesn't specifically know that information, he was merely giving examples of the types of information he has access to.
I think so too.
lionhead