Hey there, as one speaking from USALS headaches, i don't know if this post will help you, but ill post some problems i have had with various STB's.
My old Non Linux STB from Europe , i could set USALS or Diseqc but if i used the store sat position button on my remote, it would swap between USALS/Diseqc and if i had diseqc stored in the USALS, it would use that instead. - Make sure your receiver considers the Sats to use USALS and not Diseqc. Diseqc will work, but then who knows where the USALS will land up.
With my Enigma2 STB, Each satellite uses the same LNB but, i can set whether it uses Diseqc or USALS, and the configuration can be quite tedious, and you have to check/double check everything 4 times.
I also had a problem in the past where my Diseqc/USALS would get lost if i configured the channels between the STB channel editor and the back end software channel editor.
And as a final note, i have a STB that supports 4 separate coax lines. I use one dedicated to USALS. As KE4EST mentioned, diseqc switches can cause headaches....
I hope you figure it out.....