Turn Capthca on... make sure the code goes in right and it works...

I have problem with captcha,
the image is not showing up,
apart from turning it on in settings,
what else should I do to enable it?

You need to make sure the code itself is in place in your comments file. I had to put it in my main file also to make sure it worked as the comments appear directly in the body each image.
here's what the comment code looks like:
Add a comment:

<form method="post" action="<#fbself#>">
<input type="hidden" name="image" value="<#fbimagename#>" style="display: none;" />
<div class="comform">
<textarea style="width: px;" cols="40" rows="4" name="comment"><#fbcomval#></textarea>

<input style="width: px;" name="name" size="44" maxlength="20" value="<#fbnameval#>" /> Name

<input style="width: px;" name="email" size="44" maxlength="40" value="<#fbemailval#>" /> Email

<input style="width: px;" name="url" size="44" maxlength="100" value="<#fburlval#>" /> URL
<#fbcaptcha#>


<input id="submit" type="submit" value="Submit" name="doComment" /> <input id="check" type="checkbox" name="cookie" value="1" <#fbchecked#> /> Remember me</span>


This also contains the fix to make Alamanc accept comments properly..

I should mention that there are also php commands where the space before px; is in each section that the browser is hiding...

I assume I have to upgrade to FB3 for captcha to work?

Correct. It's not so bad really. There is inbuilt addressing from 2>3 so it takes care of itself. I didn't know this so just reimported the pictures. Unfortunately I lost all my Photofriday noteworthy links from this. I should really start entering there again!