We are using through-hole technology.  A few weeks ago, our board vendor
(vendor#1) changed their process(from reflow to SMOBC) on all the boards.
Since then, we started to shorts on 30-pin connector and 20-pin connectors
on one of these boards types(board A).   The 30-pin connector is also used
on a different board (board B) supplied by the same vendor.  There has not
been any problem on board B.  Before the change in the board house, board A
had an outstanding performance history of soldering process.  There has not
been any change in our wave soldering parameters.  However, there is
difference in the orientation of the 30-pin connector from board A to board
B.  Following is a try to explain the difference in graphical(?) way.

        Connector               Board           Orientation.    Direction
        =========               =====           ============    =========
                                                                     ^
        30-pin                  A               o o o o o o o ...    | 
                                                o o o o o o o ...    |

        20-pin                  A               Same as 30-pin  Same as 30-pin


        30-pin                  B               o o                  ^   
                                                o o                  |
                                                o o                  |
                                                o o                  |
                                                . .
                                                . .
                                                . .


If this doesn't make sense to you try this.

On board A, the connectors go through the wave horizontally, i.e., all the
pins on first row hit the wave and then all the pins on second row.  On
board B, 30-pin connector goes through the wave vertically.

How much difference do you think it will make if board A is rotated 90 degrees ?
What should we do to solve the problem ?

When changed to another vendor (vendor#2) for the same board (board A),
shorts went away.  Boards made by vendor#2 are also SMOBC.  However, there
is one difference in the same board made by these two vendors.  Boards from
vendor#1 has a shiny finish., where as, boards from vendor#2 has a dull
finish.  This leads me draw a conclusion that problem is limited to board A
only made by vendor#1.  

Do you think surface tension could be an issue ?

Help me.

Thanks,
Paresh.