Ok,
the HTML code is partly invalid, especially the part with the boardid input (some tags are not correctly closed).
wrong code:
<input type="hidden" name="username" value="<? echo name ?>"</
<input type="hidden" name="boardid" value="game"
</td>
<input type="submit" name="submit" value="Post Todo" />
Look at the two hidden inputs. The first one isn't closed correctly, the second not closed at all. Additionally, the table tags are not correct. Always make sure that you have correct <tr><td>...</td></tr> sequences (not something like e.g. <tr><td>...</td></td></tr></td>). Some browsers might have difficulties displaying the table correctly.
Add print_r($_POST) to the PHP code to check how the POST data looks like.
Besides that the code is a little bit dangerous and might be open to SQL injection.
Never post certain parts of a SQL query like table names or field names (or even complete SQL queries) directly with a form.
At least check if the submitted table name and user name is valid.
The hidden input with the username is some kind of dangerous, too, because users can submit whatever they want as username since you don't check if the username is valid. I'd suggest to use sessions to store certain data you need on several pages (like username/user id and stuff like that).
Thomas
