I'm going to assume that you are able to do this, and comfortable to go into your pHpMyAdmin. Once in, locate your database that WordPress is installed on. Click. On the next page you will see a structure with tables. The one that you are looking for is called wp_postmeta. Now, click on the Browse icon for wp_postmeta. On this next page click on the post_id to arrange it so that it is showing "0" as the post id. Then tick the check box, and click delete. I found the easiest way for me was to show more than 30 rows, then they were all showing as "0", I was able to "check all" hit delete and this way it was not one delete at a time.
This is just how I did it. Someone out here may have an easier method, but this worked for me. Just be sure to delete ONLY those with a post_id of "0" .. and if you're not comfortable doing this.. then don't.
Disclaimer: These directions are as-is and I take no responsibility once someone decides to go into their pHpMyAdmin. I'm simply trying to show what I did to correct this for me.