Sorry.. I was out of town..
I am using the latest version of all your modules on DNN 4.8.0
Right now I am accessing via localhost, and as I mentioned, there are other posts from other users complaining of posting messages not working, however their error message points to the exact same problem.
I am using the wall for all types on all types: profiles, events, groups, custom URL ID.. get the same problem everytime.
I also *think* I remember getting this error with one of your other modules many months ago, but think I went in to my version of the source code an fixed it myself.. don't quote me on that though :-)
jasen