There is not a lnb frequency of 9750-6000 or 5150-6000 that is valid! Either of these frequencies could be manually entered into the Gekko, but I have never seen them in a Viewsat 2000 and I doubt they exist because no lnb that I know of is set up like this.

The DMX 741u lnb has a built in diseqc switch to change from the c band to the ku band. It also has a 22 KHz switch to change from the low ku universal frequency of 9750 to the high 10600 frequency.
Valid lnb l.o. frequencies for the DMX 741u are 5150, 9750, and 10600.

There are several ways to connect this lnb to the receiver. How do you have this lnb connected? Are you using the supplied jumper? If so, then how is it connected?