Use Alt Prt screen and paste into Paint,
or if you use dropbox or One drive it will save the screen shot. 
 
Upload the picture to Imgur. 
Copy the ULR and paste into the form picture tool. 
 
Without a picture how can we help? I have all sort of vriations on white lines and whatnot. Like if I make a groove clip a white bar shows at the top.. There seems to be white lines between too. 

Here's the image.  The clip on the right is selected.
 This one does not have the 45 degree angle on the bottom white line.
 

I had a chance to do some testing this evening, and the white horizontal lines were at the top and bottom of the selected audio clip.  The lines extend the full length of the clip.  On some clips the bottom line has a 45 degree angle at each end, and the angled ends do not appear to be related to groove clip looping.  I checked in preferences->colors and I could not find anything. 
Here's the image.  The clip on the right is selected.
 This one does not have the 45 degree angle on the bottom white line.  The angled white lines on the bottom white lines are not related to the clip falling on a beat boundary.
 

I'm happy you came back! THe description has me confused. I sure hope you figure out how to get us a picture.

OOPS!. Spoke too soon. I have no idea what I'm seeing in that picture. I've never seen my display look like that. Hopefully one of the mystics around here will get you an answer.
 

If I select any clip I get a white line across the top and bottom as you describe. The 45 degree angle on the bottom line indicates that the clip has been cropped. If it was cropped from the left, the 45 degree bit will appear on the left, and if it was cropped from the right it'll appear on the right.
 

Yup, Millzy's figured it out. In Windows-speak it's known as a "focus rectangle", although SONAR only does half the rectangle so it doesn't get in the way of other graphics at the ends of clips. It's simply a way to visually indicate that a clip is selected, made more noticeable in bluegrasser's picture because there are a bunch of small clips selected. Drag a selection box around any number of clips and you'll see those lines.