Ecto Parse Error

All of a sudden, I am getting parse errors while using Ecto to check on / post to my WordPress blog. For example :

Method “metaWeblog.getRecentPosts” produced a server error: “parse error. not well formed”.

This is the full error text Ecto returns. Here is what is bizarre about the whole thing :

1. Previously rock-solid stable, and no errors.
2. I have changed nothing on my end of the connection.
3. My host claims they didn’t change anything.
4. I didn’t change any WordPress file (or any file at all) on my server, aside from posting.
5. On a separate test blog (hosted on the same server, same PHP, and same MySQL, same 2.0.6 WordPress install), everything works perfectly.

The server is reporting :

faultCode -32700
parse error. not well formed

I find a lot of half-solutions and “me too’s” on these forums, and the internet in general, but nobody has posted a specific, confirmed fix for this. Does anyone know what the fix is, and are you willing to post a specific, fully-detailed fix to this problem?

Thanks for the help !