BO SERVER DOWN HOW CAN I SOLVE PERMANENTLY

Dear Concern,

Most of the time my Business Object Server is down.

When a user want to view their webi report that time this following error generate.

Cannot Initialize Report Engine Server(Error.RWI 00226)(Error.NF)

That time I restart business object related service then the server is ok.

My question why this error occur?

How I solve this error permanently?