Presuming you have also tried scanning from a different location to rule out local interference, it looks like a trip to Uniden's Service is the next step.
I'm pretty sure Uniden has a one year warranty on new products. So if you got all your receipts, you might be okay. I can't say for sure as eBay probably isn't a Uniden vendor - that would be the only potential hitch.
Here's a link to Uniden Product repair:
Product Repair
Second to worst case scenario (not covered by warranty): Uniden would charge a flat rate repair, which I think is $49.95 plus shipping.
Worst case scenario (and real unlikely): The scanner can't be repaired. Uniden will offer a comparable model at a discounted rate and the flat rate repair cost is applied toward the cost.