One of the things about SP 2010 that has driven me crazy is the inability to get DVWPs from one level of a site to work correctly in another level. Maybe you have a list on a subsite and want to surface that content on the homepage, or the list is at the root and you want to use the DVWP on a sub site. I even went as far as having my company pay for Laura Roger’s time a year or so ago to have a web meeting with her to see if there was a solution. What I was told was that there were a few things you can try but there was no guarantee any of it would work, depending on your specific farm setup, etc. I found some instructions on the web with hacks but they never went deep enough and I could never get them to work.
Last night, as I was thinking about another dvwp issue-how to create a dvwp that displays an item randomly-I found a site that had a solution for that issue as well as one for the other issue. The problem was that the instructions still were not clear enough, there were steps that maybe were assumed but that I didn’t know about or understand. So I had to poke it a while but I finally got both issues-the random item dvwp and the make dvwp work anywhere in the site- to work.
I take no credit for these solutions, I only translated them into a more visual language for folks like myself.