Problem with tables

[hitman]

I've added a sidebar to a friend's forum, but according to the HTML validator, the start of the table code isn't connecting with the closing code and it's making the site look messed up, pushing the sidebar outside of the layout.
The sidebar works correctly on other parts of the site, except when viewing posts.

I've spent two days trying to figure out what's wrong, with no luck and would really appreciate some help. This is driving me nuts!

Attached are the image of how the messed up part of the forum looks and the text containing the code:

[felgall]

Did the sidebar work properly before you added the table into the page?

[hitman]

Did the sidebar work properly before you added the table into the page?

I did the sidebar using tables. I've added the tags cloud as a graphical mark for the location of the sidebar.

The sidebar starts with this code:
<table border="0" width="100%" cellspacing="0" cellpadding="0" align="center">
<tr>
<td valign="top">

and closes with this code

</td>
<td width="10px"></td>
<td valign="top" width="225px">
<table class="tborder" border="0" cellspacing="1" cellpadding="6" width="100%" align="center">
...tag cloud here...
</table>
</td>
</tr>
</table>

Between those two sets of codes is the body (the part on the left of the sidebar).

I've uploaded another attachment showing how it would look on the main page, as well as all the other pages on the site, except that part where it breaks

[hitman]

Anyone?

[WebJoel]

I tried to run this locally but am getting way too many runtime errors due to the path not being absolute, -is this hosted live anywhere? I would like to see it 'live' and can maybe figure something out.