Rick wrote:
As for the one or two visits that Dracula makes to Mina's room...here I must confess to being pretty wool-headed.  I've read that portion of Gary's book, and I've read Clark's explanations on the board, and I've watched the 1931 film a zillion times, and Clark's revision at least 4 times...and I just can't make heads or tails of what anybody's saying about those scenes, what's in the script, what's in the film, what was or was not lifted from another scene.  I know I'm just so damn old, but it makes me dizzy to try to figure it all out.

Rick, Dracula makes two visits to Mina's bedroom in the released version of the film. 

The first occurs 37 minutes into the film, after Van Helsing has interviewed Renfield in Steward's office, and is later explained by Mina as a dream:
DRACULA_G51.Title800.m2ts_snapshot_00.37

The second visit occurs about one hour and 7 minutes into the movie, and is when Dracula visits Mina's bedroom to abduct her and take her to Carfax Abbey.
DRACULA_G51.Title800.m2ts_snapshot_01.07

In the shooting script, and in the edits that Kerry and I have done, the first visit actually occurs much later in the film, after Renfield has joined Seward, Van Helsing, and Harker in the Library, and Seward calls Martin upstairs to tell him that Renfield has escaped again. After which Van Helsing deduces that Dracula is in the house.