Ryan,
Unfortunately, spurs like this are normal for the USB-SA44B. The frequency is usually a little higher, but it depends on your cable lengths and computer. It looked like your spurs peaked around -100 dBm with a -30 dBm reference level for a 100 MHz span.
When you use a span of 200 kHz or less, most of these spurs will be drastically reduced or eliminated. This is because the SA44B mixes differently for narrow spans.