Well, I have earlier had a hunch that one of the problems with loading the data is that my tables are color coded using VBA and not using the native built-in formatting in Excel. This issue have been raised by me in the past and I even suggested removing formatting completely, but since I didn't get a reply, I figured that wasn't the case.
But, this programmer once again complained that color formatting does take up resources. Really?
So, I suggested that they remove the VBA code and that I format my own sheets using native built-in rules in Excel. Voila. Speed is improved 10 fold and I have full control over formatting myself.
Incredible that they have been spending days trying to improve speed and couldn't figure out this on their own. Anyway, my software is working to satisfaction now.
Well ... since the basics were overlooked ... here is a list of more of them:
http://datapigtechnologies.com/blog/index.php/ten-things-you-can-do-to-speed-up-your-excel-vba-code/