Problems with domain mapping after upgrade

Initially i have a problem with an existing Marketpress installation that has stopped working. After much digging I believe this is caused by a problem caused after doing an upgrade to the Domain Mapping plugin via the WPMU Dev panel. My suspicion that Domain Mapping has become unstable is that if i go into the Domain Mapping > Mapped Domains tab the 'health status' spinner continually spins for both of my mapped sub-domains. My suspicion is there is a database issue and am trying to figure out how to reset everything. I deactivated and removed the plugin and re-installed fresh, but with same result. If i try and delete the mappings it asks me am i sure, and when i say yes nothing happens. Clearly there is a big problem. Can someone please advise me on how to overcome this issue - i am not averse to removing records in the database manually, but if the plugin authors can advise me on the schema/which records to remove that would be appreciated.