Store page suddenly is taking a long time to load 75Seconds

Need help with figuring out what has suddenly caused the "store" page to load very slowly i.e. based on some firefox plugins that help with performance there are 75Secs for the server to respond to the GET request for the store page. All other pages load okay (nothing stellar but okay). It only happens on the store page, so it appears to be marketpress related.

things I tried:
1) I have tried disabling various other plugins, but nothing helped the performance of the store page.
2) I looked for any database tables that need to be fixed or optimized, but the status of everything came back OK.
3) I tried gtmetrix to analyze the load time for the store page, but that times out and won't run.

This wasn't that bad not that long ago, but I do not know exactly when the performance tanked.

thanks in advance for any help/ideas.
So it doesn't appear to be database problem.

EDIT: I should also add that I did iadjust some settings on the site to see if that would also help, but saddly no:

wp-config.php changes
define('MP_LARGE_DOWNLOADS', true);
define('WP_MEMORY_LIMIT', '3000M');

.htaccess changes
php_value upload_max_filesize 1000M
php_value post_max_size 2000M
php_value memory_limit 3000M
php_value max_execution_time 360
php_value max_input_time 360