Simpleviewersource was written for version 1.x of Simpleviewer I think, so there's no guarantee it's compatible with 2.x. Someone will need to investigate what, if any, the differences are from the perspective of the xml data source, and if there are any changes that need to be made - and report back. That someone isn't going to be me though, sorry. In the mean time, try using a 1.x version of simpleviewer and see if that works.
I went this way and fixed XMLOut.inc which you can downoad from http://lech.as/_support/XMLOut.zip. If you replace original one with it it will give you xml proper for version 2.x
I did not perform heavy tests. It just works for me - I hope it will work for you.
I've made it aviable at: http://lech.as/_support/XMLOut.zip