First, I have no idea why your suggestion only works for some. Maybe: Word versions, OS's, settings. No idea, but it doesn't.

WORKS FOR SURE:
1. Highlight the entire table - maybe start with mouse a line above and drag to mark a line below (other things work but this is universal too)
2. Edit/Cut the table (crtl X)
3. Table is gone.
4. Add some blank lines
5. Edit/Paste
6. Table is back with some lines above it.
7. Use as normal.

comment: TechREpublic shouldn't be so greedy in getting so much info from me in order to post a comment. Maybe you lose 8 out of 10 who would otherwise reply? You need a great reason to waste peoples time. Sharing info has a lot of faces.