When calling UpdateStatus() with any of these five characters !'()* in the status text the update fails with "Could not authenticate you".
I noticed that these characters encode differently in the status in the query string and the post data (not sure why it's in two places anyway) so wondered if this had something to do with it.
I'm assuming the encoding and hashing are causing the authentication issue
Using vb.net, twitter api version 1.1
Note: There may be other characters as well but as I think it's due to url encoding I just tested this list: `!@#$%^&*()_-+=.~,:;'?/|\