Those of us who have rooted our phones and have been using Froyo for a while have been aware of this problem for a while. It affects Sirius as well as other streaming music apps like Pandora, etc.
The problem has been identified as being caused by a new multimedia decoder in 2.2 called "Stagefright". Someone discovered that if you disable Stagefright, the phone will use the older decoder and the Sirius looping/skipping problems go away.
Unfortunately doing this requires root access, as a system file (build.prop) needs to be modified.
Of course what should happen eventually is either Google fixes Stagefright, or Sirius updates their app. One or the other.
So you guys are definitely right, Sirius is giving you bogus answers. Chances are though, their CSRs simply have not been informed of the true issue yet.
Ok, kids, here is what I did. I did several searches on this forum regarding rooting and what I would need. I'm a noob to rooting so it wasn't easy, having had no interest before. Well, because I am on 2.2, that complicates things a bit. Fortunately, very recently, Easy Root came out with a version that allows you to root 2.2 with a couple of button pushes. Best $0.99 you can spend if you want to root.
Next move was to figure out how to edit the file listed above, build.prop. I went after the free Terminal Emulator first, installed it and that wouldn't run. So I saw that someone recommended Root Explorer. Another awesome purchase and highly recommended for a couple of bucks. Astro wouldn't get to the root files, so this is needed. I went into the /system folder and found the file build.prop. I pushed and held and went into the text editor, after forcing R/W access with a button. I edited the suspect line from TRUE to FALSE, backed out, was prompted to save the file. It did, as well as making a backup copy. I rebooted the phone, just in case, launched Sirius/XM app, and lo and behold, no more buffering issues!
Thanks for pointing us in the right direction on this problem. I'm happy to have the music playing correctly again!