Giving up on WCF POX for the moment

I need to get going on the completion of my api for my mobile phone project.  I created a quick and dirty proof of concept with asp.net, but my ultimate aim was to go for a full on WCF fronted api.  If all I plan on doing is some Restful url based stuff, it's awesome, I love it.  My problem is that I decided that I want to be a bit cooler than that, and actually post data from the phone and get some data back in return.  I didn't want to have the whole WCF client stuff involved because I want the api to be open for anyone to just build whatever on top of it, so I was looking at straight up HTTP and POX.

I can't seem to get it to work, I keep getting "400" errors, bad request when I do a POST to it through a test client, or a web page, or through Fiddler.  Its very disapointing because I was looking so forward to doing this in WCF, but it appears that it won't happen for this go round, and I'll have to revert to asp.net to get the job done in a timely manner.  Of course I'll write it with a quick conversion in mind in the event that I figure it all out, but it still makes me sad inside.