I came across this error while trying to publish a dashboard on a tableau server (which, until Friday, was working out fine):
In this case, the underlying data source is extracted from a SQL Server and stored on a network drive and the extract has about 500mB of storage size. However, the error persists on other dashboards and with other users, as a matter of fact. Another relevant piece of info: during the weekend, there was an attempt to upgrade the server to Tableau 10 however it didn't work and they restored the server to a backup made prior to the attempt.
When I see these sorts of issues, often the underlying cause is that the run-as account on the server doesn't have the proper permissions the Tableau Server directories. Have your admin verify these permissions: