Your theme is too narrow (or the sidebars both on the left and right are too wide). This is the relevant output
your theme:<!-- Start standard table -->
<table align="center" width="" cellspacing="0" cellpadding="0" class="maintable">
<tr>
<td valign="top" background='themes/eyeball/images/tile.gif' align="center" height='30'> </td>
</tr>
<tr>
<td valign="bottom" class="thumbnails" align="center">
<a href="displayimage.php?p=117"><img src="albums/audioslave/thumb_audioslave3.jpg" class="image" height="125" border="0" alt="audioslave3.jpg" title="Filename : audioslave3.jpg
Filesize : 30KB
Dimensions : 550x413
Date added : Apr 20, 2005"></a>
<span class="thumb_title">Chris Cornell - Audioslave – 73 views</span><span class="thumb_title"><a href ="profile.php?uid=7005">Staticfiends.com</a></span>
<a href="displayimage.php?p=116"><img src="albums/audioslave/thumb_audioslave2.jpg" class="image" height="125" border="0" alt="audioslave2.jpg" title="Filename : audioslave2.jpg
Filesize : 125KB
Dimensions : 550x733
Date added : Apr 20, 2005"></a>
<span class="thumb_title">46 views</span><span class="thumb_title"><a href ="profile.php?uid=7005">Staticfiends.com</a></span>
<a href="displayimage.php?p=115"><img src="albums/audioslave/thumb_audioslave.jpg" class="image" height="125" border="0" alt="audioslave.jpg" title="Filename : audioslave.jpg
Filesize : 95KB
Dimensions : 550x733
Date added : Apr 20, 2005"></a>
<span class="thumb_title">Chris Cornell – 62 views</span><span class="thumb_title"><a href ="profile.php?uid=7005">Staticfiends.com</a></span>
</td>
</tr>
<tr>
<td valign="top" background='themes/eyeball/images/tile.gif' align="center" height='30'> </td>
</tr>
</table>
<!-- End standard table -->
classic theme:<!-- Start standard table -->
<table align="center" width="" cellspacing="1" cellpadding="0" class="maintable">
<tr>
<td valign="top" background='themes/classic/images/tile.gif' align="center" height='30'> </td>
</tr>
<tr>
<td valign="bottom" class="thumbnails" align="center">
<a href="displayimage.php?album=20&pos=16"><img src="albums/audioslave/thumb_audioslave3.jpg" class="image" height="125" border="0" alt="audioslave3.jpg" title="Filename : audioslave3.jpg
Filesize : 30KB
Dimensions : 550x413
Date added : Apr 20, 2005"></a>
<a href="displayimage.php?album=20&pos=17"><img src="albums/audioslave/thumb_audioslave2.jpg" class="image" height="125" border="0" alt="audioslave2.jpg" title="Filename : audioslave2.jpg
Filesize : 125KB
Dimensions : 550x733
Date added : Apr 20, 2005"></a>
<a href="displayimage.php?album=20&pos=18"><img src="albums/audioslave/thumb_audioslave.jpg" class="image" height="125" border="0" alt="audioslave.jpg" title="Filename : audioslave.jpg
Filesize : 95KB
Dimensions : 550x733
Date added : Apr 20, 2005"></a>
</td>
</tr>
<tr>
<td valign="top" background='themes/classic/images/tile.gif' align="center" height='30'> </td>
</tr>
</table>
<!-- End standard table -->
The difference is obvious: in your custom theme, there's an additional <span> section. I guess you will have to wrap the whole enchilada in a <div> block with css attributes that tell the browser to align the content horizontally.
Joachim