I have more than 5 portal hosted on Shared Hosting, in all portal i am using asp access database connection. In every 5-15 days it seems problem for data connection (Internal Server Error 500)

My hosting provider is claiming that asp access can not handle mask user, is it, what should i do ?

You can ask the provider to give a more user friendly HTTP error. This would get you out of the guessing game. If there service is bad find a better provider. There are thousand of them.