Flexible layout with fixed width column and fixed width region gives an error

I receive a below error when using custom panel page with flexible layout with fixed width column and fixed width region:

warning: Division by zero in /home/thinghie/test/sites/all/modules/panels/plugins/layouts/flexible/flexible.inc on line 626.

My process of configuring flexible layout as below:
-Create a column with fixed width
-In the column just created, create a row containing regions
-In the row above, create a region and configure the region with fixed width
-Insert something to the region

When I see the panel on it's URL path I receive above error.

I greatly appreciate your help
Viet