Seems like you're using the wrong tool for the job. More than likely you're bumping up against the timeout for either a) the Database, connection etc, b) the reportserver's rendering timeout, c) IIS's timeouts etc... Perhaps if you elaborate on the business rules/reasons you're doign this we might be able to offer a suggestion for you.

Do you just need to get the data out? will XML or a CSV do? If you so might be better servers with BCP instead of SSRS. Will you users actually take the time to analyze 65k+ rows? probably not. I'm guessing this is for an import into another system, which is why I suggested BCP. Alternatively, you could use SSIS to output your data to another datasource, Txt file or others.

-Luke.