Problem Printing with Corel x5 (Black lines on designs)

Hi to all :-)

Recently i have problems when i print some of my designs in Corel X5.

I have an A3+ Laser printing Machine Konica Minolta C353 and Windows XP .

Some "Black thin lines" show up on my designs on the paper.  
I don't want to convert my designs to bitmaps in order to Print them. Because some details on the designs will not show up very well when i convert them to bitmap.
That's why i want to leave it as it is.

My Printer technician told me that it's not the machine's fault. It's the software fault. 

Can anyone help me please? What settings should i adjust in Corel Draw to fix this problem? 

Is there anything i can do in TOOLS -> OPTIONS -> GLOBAL -> PRINTING?

I am also attaching the picture of the printed paper to see what i mean below.