I have noticed that the border options available from the toolbar drop-down in Calc don't work correctly.
The following do not have any effect:
left and right
top and bottom
The following have only partial effect:
horizontals, left and right - only draws outer borders, not inner
vericals, top and bottom - same as above
The following work correctly:
Selecting any border configuration in Format > Cells > Borders works correctly though.
[Reproducible] with "LibreOffice 3.3.1 RC1 – WIN7 Home Premium (64bit) German UI [OOO330m19 (build 7 / tag 188.8.131.52)]" (I did not test all reported problems, only "left only", "top only").
Tested "left only" works fine in OOo 3.1.1 and 3.4-dev
Well, actually Cedric has already fixed this in another bug report... I can't remember the number at the moment.
Ah, found it.
*** This bug has been marked as a duplicate of bug 34226 ***