After reading and taking action on the the various post about blank thumbnails appearing in Simple Gallery Pro, I'm unable to resolve the issue of blank thumbnails which click to the actual images. Details:
-Joomla! 2.5.7 Stable
-Linux php53-v186
-Apache/2.2
-Cache is writeable
-"Owner" and GD verified with hosting company (Rackspace)
-Directory permissions have been checked and are 755
-The images are appropriately sized.
-Changed file names to all lower case, no brackets, dashes, slashes, or special characters.
-Cleaned cache.

Ironically, the free version worked fine for me on another site.  Any help deeply appreciated.

Example of problem ...larryturnerproperties.com/index.php/residential/17-599-500-jennings-3362-timer-creek-drive-reduced

Please install Admin Tools from www.akeebabackup.com/ in order to fix your permissions as they should be and then reinstall the extension.

Right permissions on all joomla sites:
755 for folders
644 for files

If this doesn't work pm me access to your backend as super admin please.

Per yesterday's PM,  repeated the Admin Tools Fix permissions and reinstalled SigPRO.  When that did not work, I send credentials for admin access.  As I'm not sure how this works, can I ask someone else for help or to escalate my request? 

Check your pms please.

Thanks, I responded. Hope you are successful now that I've given you proper credentials.

Per your instructions, Rackspace repeated what I had already done to make absolutely sure all files are 755/644.  I then used Admin Tools to fix permissions.

I immediately loaded the page but the blank thumbnails remain.  Thinking it may be a cache issue, I cleared the cache in the back end as well as my browser (google chrome).  Also tried in firefox, but the same blank images remain.

Please advise.

Please see last note and adivse.  This needs to resolve or I need to move on. Thanks.

Permissions verified by host company, repeated "Fix permissions" in Admin Tools.  Cleared cache. Blank thumbnails continue.  Am going to try the free version since it works on another site with similar parameters...latest version of Joomla, Admin tools, rocketheme template, etc. 

Am I correct that I need to uninstall SigPro first?

You may just disable it.

However, let me know what happened and when you are ready re enable the backend link you have sent in the private message in order to re check your issue.