I ran into this problem in BOXI Rel 3.0 running two clustered servers. If a report ran on server 1, it succeeded. If it ran on server 2 it failed with the error.
The servers are configured identically, and BOXI is installed the same on both, except that one is the primary CMS.
Both servers were writing to a unc address that resides on a separate file server using the Directory in the form //fileserver/directory/subdirectory/subdirectory.
Both servers execute under the service account that has admin privileges on the BOXI servers. We control access to the file server directories through AD Access Groups, and the service account has rw privileges through the Access Group to the destination directories. As a result, I leave the destination username and password blank.
After investigation, I noticed that on the server 1 CrystalReportsJobServer Metrics page, Unmanaged Disk Destination Default Settings Valid was true, whereas on server 2 it was false. Since I could see no way to change it to true, I went to the Destination page on server 2 and Removed the File System entry. After saving and closing the change, I came back in and Added it again.
That changed the Unmanaged Disk Destination Default Settings Valid to true, and the reports started working.
pgeadmin (BOB member since 2007-02-14)