Relative 'Newbie' - need help with copy/paste command problems in staff view. Thanks!

I was given a birthday gift of Music Creator 2003 a few years ago, and used it to enter notes [laboriously!] in the staff view, so I could create CDs of new music for practice for members of my male quartet, (& also for a chorale I am in), so they could hear their particular voice part emphasized, but still hear the overall music to tell how they fit into the sometimes difficult chords, key changes, etc.  It worked well, and I was able to copy and paste repeated verses, or sections with no difficulty.
   Then, about 2 years ago, I decided to purchase MC-4, partly for the Cakewalk TTS-1 Synthesizer included with it {MUCH better sound than my old Soundblaster card, (at the time) was providing}.
   However, whenever I try to copy a section, and then paste it, and I then try to add more notes beyond the pasted section, I get strange groups of multiple notes each time I try to add a single note, and I then have to spend a lot of time deleting the unwanted notes.   It's probably some simple solution, like toggling on or off something in the software, but I haven't had any luck figuring it out, yet.  Any help would really be appreciated!  [I am not a keyboard artist, so can't just play the notes in, and step-time entry seems harder, and less intuitive.]
     Thanks for any help anyone can offer,
              Jim Sullenberger [A 66yo who enjoys messin' around with MIDI control, especially to trigger our church's Rodgers 3 manual electronic pipe organ, in my spare time.]

Wow... I started with MC4 after having used CWP8 for a time. Old stuff.... I loved that old MC4....still have it too.
 
I don't know that I ever tried to copy and paste IN staff view.  I have seen some instances of extra notes showing up. I simply close the staff view and reopen it. The extra notes in my case were some sort of video display bug.
 
If I had to copy a part and paste it, I would likely go back to the original midi track which you are creating by mousing the notes into the staff. Since they appear in the track instantly, I would go to the track view and drag the mouse on the area you need to copy ....after you have set the snap to grid to the resolution you need..... sixteenths, eights, quarters, etc... then doing the copy/paste is a very simple thing and you should not end up with extra notes that way. You can then go back to staff, play through the new paste and edit is as you normally would.
 
hope this helps.