I have migrated my SIGPro over to my host (I was selfhosting on the MAMP server previously).
After looking through the forum I changed my folders so now my
Cache Folder = 775
Image Folders = 777
There was no Temp folder in my Joomla Images folder.
I did change permissions on the
tmp folder = 777 that was in Joomla.
My images all have the 644 permission on them and jpg is lower case.
When I click on the thumbnail box the image shows up just as it should.
Here's a link to one of my problem areas www.artransforms.com/joomla15/index.php?option=com_content&view=category&layout=blog&id=7&Itemid=5

You have permissions issue and you must console your hosting company.
Check by yourself too by trying accessing this image of your gallery:

www.artransforms.com/joomla15/cache/jwsigpro_cache_f105048806allsides.gif

The link doesn't work because it should be .jpg instead of .gif . I'm not sure how you got that link but if you change the link to .jpg it works just fine.

www.artransforms.com/joomla15/cache/jwsigpro_cache_f105048806allsides.jpg

I took it from the source code of your site... So please check your images names...

I am using the Simple Image Gallery Pro v2 and it works fine in our template. Recently I found another plugin which causes some problems with the gallery.
The plugin is Joomla Imagesized Plugin.

Using this plugin causes the thumbnail boxes in the gallery to become empty.

I was wondering if there is a fix for this problem?

Please provide me with a link to your site.

Can you please let me know where you found this source code on my site, because as far as I can tell my image names match up w/ the files. In my cache folder all the images are .jpg, matching the file names for the photos.
This would be very helpful to me, so I can check out what you are talking about/ see where the discrepancy might be coming from.

I took it from the source code of your site... So please check your images names...

Please provide me with a link to your site.

Sorry, currently we are running locally and can not upload the site as yet. I put down the plugin name just in case it was possible for you to use the combination of the two extensions to see if there is a problem.
Extension:
Joomla Imagesized Plugin
extensions.joomla.org/extensions/news-display/articles-summary/5738
Simple Image Gallery PRO plugin which I purchased from JoomlaWorks.

Currently I can not grant access to the site.

Your help would be greatly appreciated.

@Hobbesfrnd,
Go to your page with SIG PRO and check the View Source Code (Ctrl+U). At line 186 you will see the link I have posted you above...

@Teru, try to change pop up engine at SIG Pro. If this doesn't solve the problem... you must choose between the two plugins...