Status Code (422) unprocessable Entity using WebDAV/EXOLEDB Error

I came across a tricky situation.

One of the customer got the (422) Unprocessable Entity using WebDAV Error, when he tries to access Exchange Server 2007 for the query "SELECT “DAV:displayname” FROM “Inbox”  WHERE CONTAINS(*, '"Mike"')"...he is referring that "Use an asterisk (*) to include all properties marked for full-text indexing".

The request for working fine for Exchange Server 2003, but its not working on Exchange Server 2007. Found full-text indexing is enabled.

Requests without CONTAINS predicate work fine on Exchange 2007. He wondered what is wrong with the request?

The issue was quite confuseing...during research i found the update from Glen from one of our MSDN forum...(View the thread)

"...the Search service was rewritten in 2007 to use MSSearch v3  as WebDAV and Exoledb have been demphasised on 2007 I have a feeling that they these API's where not ported for the new search service. Either that or its a bug i can't make simple searches using WebDAV or Exoledb work."

FYI...