Alright Bud
Just stuck a sat dish up myself this weekend and had similar experience........I think your problem is your dish has become, or is, slightly misalighned therefore you are not catching the full signal on all channels.
Go to menu, installation & antenna set up.......you want your signal intesity & signal quality both lit up and giving you a reading.
You can increase your signal quality & intensity by moving your dish (by mere millimeters) either left or right and up & down. You can also give your lnb a twist left or right. Initially adjust the dish left or right and see if your signal readings improve.
It is just a slight tweak you need due being able to recieve some channels ok.
Hope this helps.......