the site is:
http://epc.voteprotect.orgClick on research/maps.
Click on the state you want, and then narrow it down to a county if you'd like. (If you don't recognize the county on the map, click on its name below the map).
You can limit your search to "machine problems," but sometimes evidence of what you're looking for can be found in other categories as well.
It's important to note the most specific information available as to the location of each complaint. It's best to have the serial number of the actual voting machines in question. Second best is to have the precinct number. Third best is to have the polling place (some have only one precinct, some have more). If you don't have any of that information, as far as I know the complaint isn't useful. Except that the Election Protection Coalition may eventually be able to help you track the complaint to the person who made it. This is complicated and there would have to be compelling need for that specific kind of evidence for it to happen.