This may not be the most appropriate forum for this question, but I'm hoping the experts with an answer are here and can help.
I have sites hosted at a hosting company. People in certain parts of the country experience intermittent periods of being unable to resolve my domain names. These periods usually don't last more than 30 minutes but can happen several times a day. The sites are up, and others are able to correctly resolve the DNS names during that time. One of the free monitoring sites, Montastic, reports it is unable to resolve the domain, so it is experiencing the same issue as these other people.
What are some of the possible causes of this intermittent problem? Are there possible misconfigurations in the DNS at my host that could cause this? Are there possible misconfigurations at those folks' service providers that could cause this?
Any information or suggestions would be greatly appreciated!