Bounce Selection Issue

New here… was wondering if anyone else is having an issue with “Bounce Selection”

Once I bounce two clips together, I get small bursts of static and silence? If I undo and re-bounce selection it seems to be okay?

I’m using both Cubase 6 and Nuendo 6.5, Windows 7 Focusrite Saffire Pro 14 Firewire card

I just went back to Windows 7 from Windows 8 but, it was also happening in windows 8 with another soundcard?

Any Ideas?

Thank you much!