This bug was created out of the bug report 75605.
It shows problems when changing the LINE STYLE of the border.

1. Open WRITER
2. Go to INSERT -> TABLE and insert a new table (2x2)
3. Place the cursor inside the table
4. Go to TABLE -> TABLE PROPERTIES -> tab BORDERS
5. Change the LINE STYLE type to simple double line (ninth from the top, two thin lines), the LINE WIDTH is kept at 0.05 pt and then press OK

Interim Result:
No double line is visible, but a thicker single line.

6. Go to TABLE -> TABLE PROPERTIES -> tab BORDERS
7. Change the LINE WIDTH to 1.75 pt by using the arrow and please pay all the time attention to the LINE STYLE

Interim Result:
When changing LINE WIDTH from 1.5 pt to 1.75 pt, the LINE STYLE changes to a double line with one thin line and one thicker line.

8. Press OK

Interim Result: 
No double line visible, but single borders with thinner and thicker lines (thin lines at the top and on the left, thick lines at the bottom and on the right).

9. Go to TABLE -> TABLE PROPERTIES -> tab BORDERS
10. Change the LINE STYLE to two single thin lines (pay attention: the offered line styles have changed!) and press OK

Interim Result:
No double lines visible, but single borders with thinner and thicker lines (thick lines at the top and on the left, thin lines at the bottom and on the right).

11. Go to TABLE -> TABLE PROPERTIES -> tab BORDERS
12. Change the LINE WIDTH to 2.75 pt and press OK

Result: 
Double lines at the top and on the left, but no double line at the bottom and no correct double line on the right.
Operating System: Windows 8
Version: 4.2.1.1 release