Is there more to his shaky performance last night?

Was there more than just nerves behind 17-year-old DAVID ARCHULETA's shaky performance on last night's "American Idol"?

The early favorite was definitely off his game and even forgot several lines during his version of THE BEATLES' "We Can Work It Out." Sources are telling ET the singer may be feeling the pressure from his "stage father" JEFF ARCHULETA, who reportedly yelled at David during a recording session Monday. Sources say Dad wasn't happy with his son's singing -- and even brought him to tears. Neither Jeff nor reps for "American Idol" would comment on the alleged incident.

Update: LYNN and ALEX, writers of entertainment blog www.laragmag.com tell ET that this may not be the first time Jeff has lost it -- they tell us that he was banned from the set of "Star Search" when a 12-year-old David competed on the program. The writers explain that there were rumors that Jeff had allegedly harassed a girl named TIFFANY who was David's competition in the contest.