I wasn't sure if this should be posted in the bugs forum or not considering it's a plugin. However, the plugin is included by default and listsed as a b2evolution feature on the website.

I just did a fresh install of b2evo and the sidebar plugin was giving me a "page not found" error when opening the side bar.

I changed lines 64 from

window.sidebar.addPanel("<?php echo T_('Post to b2evolution') ?>","<?php echo $admin_url ?>b2sidebar.php","");

to

window.sidebar.addPanel("<?php echo T_('Post to b2evolution') ?>","<?php echo $admin_url ?>?ctrl=edit&mode=sidebar","");

and line 79 from

<a href="javascript:Q='';if(top.frames.length==0)Q=document.selection.createRange().text;void(_search=open('<?php echo $admin_url ?>b2sidebar.php?popuptitle='+escape(document.title)+'&amp;popupurl='+escape(location.href)+'&amp;text='+escape(Q),'_search'))"><?php echo T_('b2evo sidebar') ?></a></p>

to

<a href="javascript:Q='';if(top.frames.length==0)Q=document.selection.createRange().text;void(_search=open('<?php echo $admin_url ?>?ctrl=edit&mode=sidebar?popuptitle='+escape(document.title)+'&amp;popupurl='+escape(location.href)+'&amp;text='+escape(Q),'_search'))"><?php echo T_('b2evo sidebar') ?></a></p>

I have tried the new IE link, but the Gecko one is working now.