It is very difficult to diagnose this type of problem without being able to view the site. If you post a link to your site, someone may be able to help you.
lol, the url is above 🙂
The image which is used is http://vicarwaterpark.org/wp-content/uploads/2011/05/logo.png.
You use an edited version of twentyten, please keep in mind your changes are overwritten when a new twentyten update comes.
I would recommend you should look into child themes, to keep your changes safe.
You should look in your theme editor (Appearrance > editor)
Find header.php and look for
<h1 id="site-title">
or the filename mentioned above.
That’s where you most likely find the code to change this.
Sorry, when a link is posted to an image, I don’t examine it to see if it is contained in the site, I look for a link to the site itself.
Create your new image as logo.png sized 103 x 72px.
Use ftp or a file manager from your hosting service to replace wp-content/uploads/2011/05/logo.png
What I posted is unrelated to each other… maybe had to mention that… saw he was using twentyten… that’s why I posted it (as well).