Alright, I wrote a giant speech about how I don't owe anyone any buttery formal courtesy, but I think it would just be wiser to remove that...
good choice. as middlesister also implied: simple courtesy will get you a lot further than discourtesy ever will. when you use FREE software and ask for FREE support from VOLUNTEERS you can be assured that you will find people a lot more interested in helping you if you are courteous.
Alright, the way I'm gonna say this is blunt, but I assure you I am *not* being rude or impatient here. I'm just a blunt person. I don't judge people for the way they communicate, so please don't judge me.
on the internet you only have the written word as context. so what you write is ALL that we have to go on. english as a second language is usually obvious, but i have no way of knowing that your apparent rudeness rudeness is rooted in your autism and isn't intentional.
i wasn't grievously offended, i mean it is the internet so I don't really care, but i wasn't really interested in bothering to help you either.
but since that is cleared up, we can get back on topic:
if you take a look at:
this is running the latest stable release of thematic from the link provided in my earlier post. not a child theme, so no adjustments. you'll see the first post "A Video Post" is showing a thumbnail. all i had to do for this to happen was set a featured image when creating my post. this works automatically anywhere thematic is using excerpts (which is on every archive) unless you make a change... such as setting thumbnails to false in your child theme, or filtering thematic_post.
but if you go here:
you'll see that the same post is not showing a thumbnail. the home/blog page is set to show full posts by default. you can change this w/ function
$content = "excerpt";
middlesister also mentioned the <!--more--> tag. so you are on the home/blog page and use a more tag, you are still showing the full content, just clipped and NOT the excerpt.
if this isn't working, then my debug process... is to disable all plugins and remove all the functions from your functions.php. then you slowly add the pieces back until you discover which one was the culprit.
lastly, another tip to get better help is to provide a link. i know i work on a local install usually, but it helps us help you to see what is happening. a picture is worth a thousand words and all that. plus markup is worth more when debugging.