Have you checked that in device manager and SB that both are set the same (Try using com 4 in both)
Also have you checked comm settings in SB.
Baud Rate - 9600
Data Bits - 8
Parity - None
Flow control - Hardware
Also make sure the above is the same in device manager.
You will need to right click the com port in device manager to check that.
Sounds to me you haven't got everything synced together to work.
I've been extremely plasec with Clean Cut 60degree blades in my Graphtec. They last longer for me, and I think I get a littler better quality on the very small fine cuts.