Explicitly set the height and width of the blocktype images.

This is necessary because when the javascript to create the clones is being run, the images may not have been downloaded, so the height the clone will be set to will be only the height of the title and description. This leads to blocks that you can only drag from the top part.

This was hard to track down because subsequent requests had the cached images ready to insert.

htdocs/theme/default/templates/view/blocktypelist.tpl

@@ -3,7 +3,9 @@
 {foreach from=$blocktypes item=blocktype}
     <li>
         <div class="blocktype">
-            <img src="{$blocktype.thumbnail_path | escape}" alt="{str tag='preview'}">
+            {* The width and height are required so that the javascript that places the clones knows how
+               big it should make itself. Talk to Nigel before changing this *}
+            <img src="{$blocktype.thumbnail_path | escape}" alt="{str tag='preview'}" width="70" height="58">
             <h3>{$blocktype.title | escape}</h3>
             <p>{$blocktype.description | escape}</p>
             <input type="{if $javascript}hidden{else}radio{/if}" class="blocktype-radio" name="blocktype" value="{$blocktype.name | escape}">