Try with this:
PHP Code:
<a href="http://twitter.com/home/?status=http://www.forum.com/{vb:link thread, {vb:raw thread}, {vb:raw pageinfo_post}}#post{vb:raw post.postid}" target="_blank">
<img src="http://www.forum.com/images/bookmark/twitter_32.png" alt="Share in twitter" style="border-style: none"/>
</a>
This will share the current post link and will be converted to vBSEo links as well.
I've included a image wich can be used with this post at 32px but you can use any image that you want.
- Rafael