trailing /? added to confirmation redirect

I've got a problem with the confirmation redirect adding a /? to the end of the designated page.
Example:
When you fill out the first form on this page:
http://www.adhdcoaches.org/acce-kubik/
the professional registration redirects to
http://www.adhdcoaches.org/po-kubik-m/?

Sometimes *I* get the page as it should be, other times my experience matches the complaints from users saying that they get a blank where the post/content should be.

Using Firefox Live HTTP Header add on, the header shows
XML-RPC server accepts POST requests only.
(I don't really know what that means)(S)

Some things I've read seem to imply that this could be a problem with the cache. But no specific cache plugin is installed. Some conversations I've had with my guys suggest a problem with the Apache handler.

I have done the "switch to the twenty ten" theme... same problem.
and the turn off all the other plugins... same problem
I tried making a new form with the same redirect confirmation, same problem.

I tried changing the permalink structure to test the problem as suggested here:
http://www.gravityhelp.com/forums/topic/form-not-submitting#post-2233

However, when I set the permalinks to default (which given the ? might imply that's where the problem is) they don't change. They stay as domain/post-name

When I change it back.. I get the message that the .htaccess is not writeable .. I changed the chmod to 777 .. still not writeable.
I manually changed the .htaccess

<IfModule mod_rewrite.c>
RewriteEngine On
RewriteBase /
// [the following line was not included before] (and no, this line is not in the actual file)
RewriteRule ^index\.php$ - [L]
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule . /index.php [L]
</IfModule>

That's all I've got about that problem.
However, here's some other stuff that happened:

I had some trouble after the last WP upgrade adding weird characters. But I found that the DB_CHARSET did not match the set shown on the mysql database. I changed the DB_CHARSET to utf8_unicode_ci and that fixed the weird character problem.

But is it possible there could be a problem with the DB_CHARSET?
See my post about that here: http://bit.ly/mc6Ha9

I'm at a loss for where to look next (or better to fix this problem!)
Thanks
kerch
http://www.adhdcoaches.org