Magento admin interface
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Navigated to - System> Cache Management
Disabled All cache
Saved Settings

Navigated to - System> Configuration > Catalog
Use Flat Catalog set to “NO”
Saved Settings

Magento .htaccess
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memory_limit = 1024M

VPS settings PHP.ini
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memory_limit =1024M

Restart VPS

Magento backend > System > Profiles > My Profile
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bucket size set to 500

Taken from David084: http://www.experts-exchange.com